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                                                                     Exhibit 3.1

                           SIXTH RESTATED CERTIFICATE

                       OF INCORPORATION OF NITROMED, INC.

     NITROMED, INC. ("Corporation"), a Corporation organized and existing under
and by virtue of the General Corporation Law of the State of Delaware (the
"General Corporation Law"), hereby certifies as follows:

     FIRST: The name of the Corporation is NitroMed, Inc. A Certificate of
Incorporation of the Corporation originally was filed by the Corporation with
the Secretary of State of the State of Delaware on March 9, 1992. A Restated
Certificate of Incorporation of the Corporation was filed on December 2, 1993
and was amended on July 27, 1994 and December 20, 1994. A Second Restated
Certificate of Incorporation was filed on June 19, 1995, and was amended on
January 10, 1996, April 11, 1996, September 30, 1996, December 17, 1996,
February 10, 1997, April 4, 1997, April 7, 1997 and July 31, 1997. A Third
Restated Certificate of Incorporation was filed on December 31, 1997. A Fourth
Restated Certificate of Incorporation was filed on May 17, 1999, and was amended
on May 1, 2000. A Fifth Restated Certificate of Incorporation was filed on May
22, 2001, and was amended on June 15, 2001.

     SECOND: This Sixth Restated Certificate of Incorporation restates and
integrates and further amends the Fifth Restated Certificate of Incorporation of
the Corporation, was duly adopted by the Board of Directors of the Corporation
in accordance with the provisions of Sections 242 and 245 of the Delaware
General Corporation Law, and was approved by written consent of the stockholders
of the Corporation given in accordance with the provisions of Section 228 of the
Delaware General Corporation Law (prompt notice of such action having been given
to those stockholders who did not consent in writing).

     THIRD: The text of the Fifth Restated Certificate of Incorporation of the
Corporation is hereby restated and amended to read in its entirety as follows:

                                    ARTICLE I

                                      NAME

     The name of the Corporation is NitroMed, Inc.

                                   ARTICLE II

                                     PURPOSE

     The Corporation is organized to engage in any lawful act or activity for
which a corporation may be organized under the General Corporation Law of the
State of Delaware.

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                                   ARTICLE III

                                  CAPITAL STOCK

     (a)  AUTHORIZATION. The total number of shares of all classes of stock
which the Corporation shall have authority to issue is 49,988,509, consisting
of:

          (i)   31,911,969 shares of Preferred Stock, par value $.01 per share
(the "Preferred Stock"), of which:

                (A)  5,000,000 shares shall be designated "Series A Convertible
Preferred Stock" (the "Series A Stock"),

                (B)  17,005,330 shares shall be designated "Series B Convertible
Preferred Stock" (the "Series B Stock"),

                (C)  3,157,895 shares shall have been designated "Series C
Convertible Preferred Stock" (the "Series C Stock"),

                (D)  2,137,791 shares shall have been designated "Series D
Convertible Preferred Stock" (the "Series D Stock"),

                (E)  4,360,953 shares shall have been designated "Series E
Convertible Preferred Stock" (the "Series E Stock");

                (F)  250,000 shares shall have been designated "Series F Junior
Convertible Preferred Stock" (the "Series F Junior Stock"); and

          (ii)  18,076,540 shares of Common Stock, par value $.01 per share (the
"Common Stock").

     (b)  The Preferred Stock may be issued in any number of series, including
without limitation the Series A Stock, Series B Stock, Series C Stock, Series D
Stock, Series E Stock, Series F Junior Stock and any other series designated by
the Board of Directors of the Corporation (the "Board of Directors") pursuant to
Section B.1, subject to Section A.6(c) hereof.

                         PART A. SERIES PREFERRED STOCK

     A.1  DESIGNATION. The Series A Stock, Series B Stock, Series C Stock,
Series D Stock, Series E Stock and Series F Junior Stock are sometimes
collectively referred to herein as the "Series Preferred Stock." The Series A
Stock, Series B Stock, Series C Stock and Series D Stock are sometimes
collectively referred to herein as the "Series A, B, C and D Preferred Stock."
The number of shares, powers, terms, conditions, designations, preferences and
privileges, relative, participating, optional and other special rights, and
qualifications, limitations and restrictions, if any, of the Series Preferred
Stock shall be as set forth herein.

     A.2  RANKING. The Corporation's Series Preferred Stock shall rank, as to
dividends and upon Liquidation (as defined in Section A.4(b) hereof), in the
manner set forth in this Sixth

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Restated Certificate of Incorporation except as otherwise approved by the
affirmative vote or consent of the holders of shares of Series Preferred Stock
pursuant to Section A.6(c) hereof.

     A.3  DIVIDEND PROVISIONS.

          A.3(a)     The holders of shares of Series E Stock shall be entitled
to receive, out of funds legally available therefor, dividends of $0.5763 per
share per annum (subject to appropriate adjustment in the event of any stock
dividend, stock split, combination or other similar recapitalization affecting
such shares), payable when and as declared by the Board of Directors of the
Corporation. Such dividends shall accrue and shall be cumulative from the date
of issuance of each share of Series E Stock, whether or not declared. The
Corporation shall not declare or pay any dividend on shares of Series A, B, C
and D Preferred Stock, Series F Junior Stock or Common Stock until the holders
of Series E Stock then outstanding shall have first received a dividend at the
rate specified in this Section A.3(a).

          A.3(b)     The holders of shares of Series Preferred Stock shall be
entitled to receive, when and as declared or paid by the Board of Directors on
any shares of Series Preferred Stock, out of funds legally available for that
purpose, dividends and distributions (whether in cash, property or securities of
the Corporation, including subscription or other rights to acquire securities of
the Corporation). Whenever any dividend may be declared or paid on any shares of
Series Preferred Stock (other than dividends on Series E Stock declared or paid
pursuant to Section A.3(a)), the Board of Directors shall also declare and pay a
dividend on the same terms, at the same rate and in like kind upon each other
share of the Series Preferred Stock then outstanding, so that all outstanding
shares of Series Preferred Stock will participate equally with each other
ratably per share (calculated as provided in Section A.3(c) hereof). Whenever
any dividend, whether in cash or property or in securities of the Corporation
(or subscription or other rights to purchase or acquire securities of the
Corporation), may be declared or paid on: (i) any shares of the Common Stock,
the Board of Directors shall also declare and pay a dividend on the same terms,
at the same rate and in like kind upon each share of the Series Preferred Stock
then outstanding so that all outstanding shares of Series Preferred Stock will
participate in such dividend ratably with such shares of Common Stock
(calculated as provided in Section A.3(c) hereof); or (ii) any shares of
Preferred Stock (other than the Series Preferred Stock), the Board of Directors
shall also declare and pay a dividend on the same terms, at the same or
equivalent rate (based on the number of shares of Common Stock into which such
Preferred Stock is then convertible, if applicable, or, otherwise, the relative
liquidation preference per share, as compared with the Series Preferred Stock
then outstanding) and in like kind upon each share of Series Preferred Stock
then outstanding, so that all Series Preferred Stock will participate in such
dividend ratably with such other shares of Preferred Stock.

          A.3(c)     In connection with any dividend declared or paid hereunder,
each share of Series Preferred Stock shall be deemed to be that number of shares
(including fractional shares) of Common Stock into which it is then convertible,
rounded up to the nearest one-tenth of a share. No fractional shares of capital
stock shall be issued as a dividend hereunder. The Corporation shall pay a cash
adjustment for any such fractional interest in an amount equal to the fair
market value thereof on the last Business Day (as defined in Section A.8 hereof)
immediately preceding the date for payment of dividends, as determined by the
Board of Directors in good faith.

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     A.4  LIQUIDATION RIGHTS.

          A.4(a)     With respect to rights on Liquidation (as defined in
Section A.4(b) hereof), the Series Preferred Stock shall rank in the manner set
forth in this Sixth Restated Certificate of Incorporation, except as otherwise
approved by the affirmative vote or consent of the holders of Series Preferred
Stock pursuant to Section A.6(c) hereof.

          A.4(b)     In the event of any liquidation, dissolution or winding-up
of the affairs of the Corporation (each, a "Liquidation"), the holders of shares
of Series E Stock then outstanding (the "Series E Preferred Stockholders") shall
be entitled to receive out of the assets of the Corporation legally available
for distribution to its stockholders, whether from capital, surplus or earnings,
before any payment shall be made to the holders of Series A, B, C and D
Preferred Stock, Series F Junior Stock, Common Stock or any other class or
series of stock ranking on Liquidation junior to such Series E Stock, an amount
per share equal to the Original Purchase Price (as defined in Section A.8
hereof), plus, in each case, an amount equal to any accrued or declared but
unpaid dividends thereon pursuant to Section A.3(a) and A.3(b) hereof.

          A.4(c)     If, upon any Liquidation, the assets of the Corporation
available for distribution to its stockholders shall be insufficient to pay the
Series E Preferred Stockholders the full amount as to which each of them shall
be entitled, then the Series E Preferred Stockholders shall share ratably in any
distribution of assets according to the respective amounts which would be
payable to them in respect of the shares held upon such distribution if all
amounts payable on or with respect to such shares were paid in full. For
purposes of calculating the amount of any payment to be paid upon any such
Liquidation, each share of Series E Stock shall be deemed to be that number of
shares (including fractional shares) of Common Stock into which it is then
convertible, rounded to the nearest one-tenth of a share.

          A.4(d)     In the event of any Liquidation, after payment shall have
been made to the Series E Preferred Stockholders of the full amount to which
they shall be entitled pursuant to Section A.4(b), the holders of shares of
Series A, B, C and D Preferred Stock then outstanding (the "Series A, B, C and D
Preferred Stockholders") shall be entitled to receive out of the assets of the
Corporation legally available for distribution to its stockholders, whether from
capital, surplus or earnings, before any payment shall be made to the holders of
Series F Junior Stock, Common Stock or any other class or series of stock
ranking on Liquidation junior to such Series A, B, C and D Preferred Stock, an
amount per share equal to the Original Purchase Price (as defined in Section A.8
hereof), plus, in each case, an amount equal to any declared but unpaid
dividends thereon pursuant to Section A.3(b) hereof.

          A.4(e)     If, upon any Liquidation, the assets of the Corporation
available for distribution to its stockholders shall be insufficient to pay the
Series A, B, C and D Preferred Stockholders the full amount as to which each of
them shall be entitled, then the Series A, B, C and D Preferred Stockholders
shall share ratably in any distribution of assets according to the respective
amounts which would be payable to them in respect of the shares held upon such
distribution if all amounts payable on or with respect to such shares were paid
in full. For purposes of calculating the amount of any payment to be paid upon
any such Liquidation, each share of Series A, B, C and D Preferred Stock shall
be deemed to be that number of shares

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(including fractional shares) of Common Stock into which it is then convertible,
rounded to the nearest one-tenth of a share.

          A.4(f)     In the event of any Liquidation, after payment shall have
been made to each of the Series E Preferred Stockholders and the Series A, B, C
and D Stockholders of the full amount to which they shall be entitled pursuant
to Sections A.4(b) and A.4(d), the holders of shares of Series F Junior Stock
then outstanding (the "Series F Junior Preferred Stockholders" and, together
with the Series E Preferred Stockholders and the Series A, B, C and D Preferred
Stockholders, the "Series Preferred Stockholders") shall be entitled to receive
out of the assets of the Corporation legally available for distribution to its
stockholders, whether from capital, surplus or earnings, before any payment
shall be made to the holders of Common Stock or any other class or series of
stock ranking on Liquidation junior to such Series F Junior Stock, an amount per
share equal to the Original Purchase Price (as defined in Section A.8 hereof),
plus, in each case, an amount equal to any declared but unpaid dividends thereon
pursuant to Section A.3(b) hereof.

          A.4(g)     If, upon any Liquidation, the assets of the Corporation
available for distribution to its stockholders shall be insufficient to pay the
Series F Junior Preferred Stockholders the full amount as to which each of them
shall be entitled, then the Series F Junior Preferred Stockholders shall share
ratably in any distribution of assets according to the respective amounts which
would be payable to them in respect of the shares held upon such distribution if
all amounts payable on or with respect to such shares were paid in full. For
purposes of calculating the amount of any payment to be paid upon any such
Liquidation, each share of Series F Junior Stock shall be deemed to be that
number of shares (including fractional shares) of Common Stock into which it is
then convertible, rounded to the nearest one-tenth of a share.

          A.4(h)     In the event of any Liquidation, after payment shall have
been made to the Series Preferred Stockholders of the full amount to which they
shall be entitled pursuant to Sections A.4(b), A.4(d) and A.4(f), with respect
to each other class or series of capital stock (other than Common Stock) ranking
on Liquidation junior to such Series Preferred Stock (in descending order of
seniority), the Series Preferred Stockholders, as a class, shall be entitled to
receive an amount equal (and in like kind) to the aggregate preferential amount
fixed for each such junior class or series of capital stock, which amount shall
be distributed among the Series Preferred Stockholders in an equal amount per
share of the Series Preferred Stock then outstanding. If, upon any Liquidation,
the assets of the Corporation available for distribution to its stockholders
shall be insufficient to pay the Series Preferred Stockholders and a class or
series of capital stock (other than the Common Stock) junior to the Series
Preferred Stock the full amounts to which they shall be entitled pursuant to the
next preceding sentence, the holders of the Series Preferred Stock and such
other class or series of capital stock shall share ratably in any distribution
of assets according to the respective preferential amounts fixed for the Series
Preferred Stock (pursuant to Section A.4(b), A.4(d) and A.4(f)) and such junior
class or series of capital stock which would be payable in respect of the shares
held by them upon such distribution if all amounts payable on or with respect to
such shares were paid in full.

          A.4(i)     In the event of any Liquidation, after payments shall have
been made to the Series Preferred Stockholders of the full amount to which they
shall be entitled as aforesaid, and after all preferential payments shall have
been made to each junior class or series of capital

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stock as aforesaid, the Series Preferred Stockholders as a class shall be
entitled to share ratably (calculated with respect to such Series Preferred
Stock as provided in the next sentence) with the holders of Common Stock (the
"Common Stockholders") in all remaining assets of the Corporation available for
distribution to its stockholders. For purposes of calculating the amount of any
payment to be paid upon any such Liquidation, each share of such Series
Preferred Stock shall be deemed to be that number of shares (including
fractional shares) of Common Stock into which it is then convertible, rounded to
the nearest one-tenth of a share.

          A.4(j)(i)  In the event of and simultaneously with the closing of an
Event of Sale (as hereinafter defined), the Corporation shall (unless waived
pursuant to Section A.4(j)(v) or otherwise prevented by law) redeem all of the
shares of Series Preferred Stock then outstanding for a cash amount per share
determined as set forth herein (the "Special Liquidation Price," said redemption
being referred to herein as a "Special Liquidation"). For all purposes of this
Section A.4(j), the Special Liquidation Price shall be equal to that amount per
share which would be received by each Series Preferred Stockholder if, in
connection with an Event of Sale, all the consideration paid in exchange for the
assets or the shares of capital stock (as the case may be) of the Corporation
were actually paid to and received by the Corporation and the Corporation were
immediately thereafter liquidated and its assets distributed pursuant to
Sections A.4(a) through (i) hereof. To the extent that one or more redemptions
(as described in Section A.5 hereof) and/or Special Liquidations are occurring
concurrently, the Special Liquidation under this Section A.4(j) shall be deemed
to occur first. The date upon which the Special Liquidation shall occur is
sometimes referred to herein as the "Special Liquidation Date."

                     A.4(j)(ii)      At any time on or after the Special
Liquidation Date, a Series Preferred Stockholder shall be entitled to receive
the Special Liquidation Price for each such share of Series Preferred Stock
owned by such holder. Subject to the provisions of Section A.4(j)(iii) hereof,
payment of the Special Liquidation Price will be made upon actual delivery to
the Corporation or its transfer agent of the certificate representing such
shares of Series Preferred Stock.

                     A.4(j)(iii)     If on the Special Liquidation Date less
than all the shares of Series Preferred Stock then outstanding may be legally
redeemed by the Corporation, the Special Liquidation shall be pro rata with
respect to such Series Preferred Stock based upon the number of outstanding
shares of Series Preferred Stock then owned by each holder thereof.

                     A.4(j)(iv)      On and after any Special Liquidation Date,
all rights in respect of the shares of Series Preferred Stock to be redeemed
shall cease and terminate except the right to receive the applicable Special
Liquidation Price as provided herein, and such shares of Series Preferred Stock
shall no longer be deemed to be outstanding, whether or not the certificates
representing such shares of Series Preferred Stock have been received by the
Corporation; PROVIDED, HOWEVER, that, if the Corporation defaults in the payment
of the Special Liquidation Price with respect to any Series Preferred Stock, the
rights of the holder(s) thereof with respect to such shares of Series Preferred
Stock shall continue until the Corporation cures such default.

                     A.4(j)(v)       Anything contained herein to the contrary
notwithstanding, the provisions of this Section A.4(j) may be waived by the
holders of at least sixty-five percent

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(65%) in voting power of the shares of Series Preferred Stock then outstanding,
by delivery of written notice of waiver to the Corporation prior to the closing
of any Event of Sale, in which event the Corporation shall not redeem any shares
of Series Preferred Stock pursuant to this Section A.4(j).

                     A.4(j)(vi)      Any notice required to be given to the
holders of shares of Series Preferred Stock pursuant to Section A.7(f) hereof in
connection with an Event of Sale shall include a statement by the Corporation of
(A) the Special Liquidation Price which each Series Preferred Stockholder shall
be entitled to receive upon the occurrence of a Special Liquidation under this
Section A.4(j) and (B) the extent to which the Corporation will, if at all, be
legally prohibited from paying each holder of Series Preferred Stock the Special
Liquidation Price.

                     A.4(j)(vii)     For purposes of this Section A.4(j), an
"Event of Sale" shall mean (A) the merger or consolidation of the Corporation
into or with another corporation, partnership, joint venture, trust or other
entity, or the merger or consolidation of any corporation into or with the
Corporation (in which consolidation or merger the stockholders of the
Corporation receive distributions of cash or securities as a result of such
consolidation or merger in complete exchange for their shares of capital stock
of the Corporation), or (B) the sale or other disposition of all or
substantially all the assets of the Corporation unless, upon consummation of
such merger, consolidation or sale of assets, the holders of voting securities
of the Corporation immediately prior to such transaction continue to own
directly or indirectly not less than a majority of the voting power of the
surviving corporation.

     A.5  REDEMPTION.

          A.5(a)     At the request of the holder or holders of at least sixty
five percent (65%) of the shares of Series Preferred Stock then outstanding
(individually, a "Requesting Holder" and, collectively, the "Requesting
Holders") made at any time after December 31, 2003, the Corporation shall redeem
on the Redemption Date (as such term is defined in Section A.5(c) hereof)
(unless otherwise prevented by law), at a redemption price per share equal to
the Original Purchase Price (as defined in Section A.8), plus an amount equal to
any declared but unpaid dividends thereon, up to thirty three and one-third
percent (33 1/3rd %) of the shares of each such series of the Series Preferred
Stock owned of record by such Requesting Holder at the time that such request is
made, and in each subsequent year thereafter (upon the anniversary of the
Redemption Date) up to thirty three and one-third percent (33 1/3rd %) of the
shares of each such series of the Series Preferred Stock that was owned of
record by such Requesting Holder on the Redemption Date plus that number of
shares of each such series of Series Preferred Stock that such Requesting Holder
could have required the Corporation to have redeemed in the year or years
following the Redemption Date pursuant to this Section A.5(a), but elected not
to have redeemed. Each Requesting Holder who desires to have any of the Series
Preferred Stock owned of record by such Requesting Holder redeemed shall specify
in a written notice to the Corporation the number of shares which the Requesting
Holder elects to redeem (a "Redemption Notice"), in accordance with Section
A.5(c) hereof. The total sum payable per share of Series Preferred Stock on the
Redemption Date or on the subsequent anniversaries of the Redemption Date, as
the case may be, is hereinafter referred to as the "Redemption Price," and the
payment to be made on the Redemption Date is hereinafter referred to as the
"Redemption Payment."

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     Notwithstanding any limitations specified in this Section A.5, in the event
that the Corporation at any time breaches any of its representations,
warranties, covenants and/or agreements set forth in:

                (i)    that certain Fourth Amended and Restated Stockholders'
Agreement dated May 22, 2001, as amended, among the Corporation and the persons
or entities listed on Schedule 1 thereto (the "Stockholders' Agreement"); or

                (ii)   in the case of the holders of Series A Stock that certain
Series A Convertible Preferred Stock Purchase Agreement dated December 3, 1993
(the "Series A Stock Purchase Agreement"); or

                (iii)  in the case of the holders of Series B Stock, either (A)
that certain Series B Convertible Preferred Stock Purchase Agreement dated June
20, 1995 or (B) that certain Series B Convertible Preferred Stock Purchase
Agreement dated April 4, 1997, as the case may be; or

                (iv)   in the case of holders of Series C Stock, that certain
Series C Convertible Preferred Stock Purchase Agreement dated December 31, 1997
(the "Series C Stock Purchase Agreement"); or

                (v)    in the case of holders of Series D Stock, that certain
Series D Convertible Preferred Stock Purchase Agreement dated May 17, 1999 (the
"Series D Stock Purchase Agreement"); or

                (vi)   in the case of holders of Series E Stock, that certain
Series E Convertible Preferred Stock Purchase Agreement dated May 22, 2001 (the
"Series E Stock Purchase Agreement"); or

               (vii)   in the case of holders of Series F Junior Stock, that
certain Series F Convertible Preferred Stock Purchase Agreement dated November
20, 2001 (the "Series F Stock Purchase Agreement"),

then the holders of at least sixty-five percent (65%) of the shares of Series A
Stock, and/or Series B Stock, and/or Series C Stock, and/or Series D Stock,
and/or Series E Stock, and/or Series F Junior Stock, as the case may be, then
outstanding shall have the right to elect, at their sole discretion, if any such
breach is not cured by the 60th day after receipt by the Corporation of notice
of such breach from a holder of Series A Stock, and/or Series B Stock, and/or
Series C Stock, and/or Series D Stock, and/or Series E Stock, and/or Series F
Junior Stock, as the case may be, to accelerate the maturity of their rights
under this Section A.5 and immediately redeem all, but not less than all, of the
issued and outstanding shares of Series A Stock, and/or Series B Stock, and/or
Series C Stock, and/or Series D Stock, and/or Series E Stock, and/or Series F
Junior Stock, as the case may be. With respect to a breach of which the
Corporation is aware or reasonably should be aware, such 60-day period within
which the Corporation shall have the right to cure such breach shall be deemed
to have commenced on the tenth day after the occurrence of such breach,
irrespective of notice of such breach from a holder of Series A Stock, and/or
Series B Stock, and/or Series C Stock, and/or Series D Stock, and/or Series E
Stock, and/or Series F Junior Stock, as the case may be, if the Corporation
shall not have notified the

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holders of Series A Stock, and/or Series B Stock, and/or Series C Stock, and/or
Series D Stock, and/or Series E Stock, and/or Series F Junior Stock, as the case
may be, of such breach by such date.

          A.5(b)     On and after the Redemption Date, all rights of any
Requesting Holder with respect to those shares of Series Preferred Stock being
redeemed by the Corporation pursuant to Section A.5(a), except the right to
receive the Redemption Price per share of Series Preferred Stock as hereinafter
provided, shall cease and terminate, and such shares of Series Preferred Stock
shall no longer be deemed to be outstanding, whether or not the certificates
representing such shares have been received by the Corporation; PROVIDED,
HOWEVER, that, notwithstanding anything to the contrary set forth herein, (A) if
the Corporation defaults in the payment of the Redemption Payment, the rights of
the Requesting Holder with respect to such shares of Series Preferred Stock
shall continue until the Corporation cures such default, and (B) without
limiting any other rights a Requesting Holder, upon the occurrence of a
subsequent Liquidation or Event of Sale, with respect to the shares of Series
Preferred Stock in respect of which no Redemption Payment has been received by a
Requesting Holder, such Requesting Holder shall be accorded the rights and
benefits set forth in Section A.4 hereof in respect of such remaining shares, as
if no prior redemption request had been made.

          A.5(c)     Each Requesting Holder shall send its Redemption Notice
pursuant to this Section A.5 by first class, certified mail, return receipt
requested, postage prepaid, to the Corporation at its principal place of
business or to any transfer agent of the Corporation. Within five (5) business
days of receipt of a Redemption Notice, the Corporation shall notify in writing
all other Series Preferred Stockholders of the request by a Requesting Holder
for the redemption of Series Preferred Stock (the "Corporation Notice"). If any
other Series Preferred Stockholder desires to have redeemed all or any portion
of the Series Preferred Stock owned of record by such Series Preferred
Stockholder, each such Series Preferred Stockholder shall send a Redemption
Notice to the Corporation postmarked within five (5) business days after the
receipt of the Corporation Notice, and such Series Preferred Stockholder shall
be deemed to be a Requesting Holder. On the twentieth (20th) business day
following the date upon which the Corporation received the first Redemption
Notice from a Requesting Holder, the Corporation shall pay each Requesting
Holder the applicable Redemption Price pursuant to the terms of Section A.5(a),
provided that the Corporation or its transfer agent has received the
certificate(s) representing the shares of Series Preferred Stock to be redeemed.
Such payment date shall be referred to herein as the "Redemption Date." If, on
the Redemption Date, less than all the shares of Series Preferred Stock
requested to be redeemed may be legally redeemed by the Corporation, the
redemption of such Series Preferred Stock shall be PRO RATA based upon the
number of shares of Series Preferred Stock requested to be redeemed by each
Requesting Holder thereof, subject to the thirty three and one-third percent
(33 1/3rd %) limitation set forth in Section A.5(a) hereof, if applicable, and
any shares of Series Preferred Stock not redeemed shall be redeemed, at the
holder's election, on any date following such Redemption Date on which the
Corporation may lawfully redeem such shares, again subject to such thirty three
and one-third percent (33 1/3rd %) limitation, if applicable. The Corporation
shall redeem (unless otherwise prevented by law) the shares of Series Preferred
Stock being redeemed by each Requesting Holder on the Redemption Date and the
Corporation shall promptly advise each Requesting Holder of such Redemption Date
or of the relevant facts applicable thereto preventing such redemption. Upon
redemption of only a portion of the number of shares covered by a Series
Preferred Stock certificate, the

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Corporation shall issue and deliver to or upon the written order of the holder
of such Series Preferred Stock certificate, at the expense of the Corporation, a
new certificate covering the number of shares of the Series Preferred Stock
representing the unredeemed portion of the Series Preferred Stock certificate,
which new certificate shall entitle the holder thereof to all the rights, powers
and privileges of a holder of such shares.

          A.5(d)     Shares of the Series Preferred Stock are not subject to or
entitled to the benefit of any sinking fund.

     A.6  VOTING.

          A.6(a)     In addition to any other rights provided for herein or by
law, the Series Preferred Stockholders shall be entitled to vote, together with
the Common Stockholders as one class, on all matters as to which Common
Stockholders shall be entitled to vote, in the same manner and with the same
effect as such Common Stockholders. In any such vote, each share of Series
Preferred Stock shall entitle the holder thereof to the number of votes per
share that equals the number of shares of Common Stock (including fractional
shares) into which each such share of Series Preferred Stock is then
convertible, rounded up to the nearest one-tenth of a share.

          A.6(b)(i)  In addition to the rights specified in Section A.6(a), the
holders of a majority in voting power of the Series Preferred Stock, voting as a
separate class, shall have the exclusive right to elect five (5) members to the
Board of Directors (the "Preferred Directors"). In any election of Preferred
Directors pursuant to this Section A.6(b), each Series Preferred Stockholder
shall be entitled to one vote for each share of the Series Preferred Stock held,
and no Series Preferred Stockholder shall be entitled to cumulate its votes by
giving one candidate more than one vote per share. The exclusive voting right of
the Series Preferred Stockholders contained in this Section A.6(b)(i) may be
exercised at a special meeting of the Series Preferred Stockholders called as
provided in accordance with the By-laws of the Corporation, at any annual or
special meeting of the stockholders of the Corporation, or by written consent of
such Series Preferred Stockholders in lieu of a meeting. The Preferred Directors
elected pursuant to this Section A.6(b) shall serve from the date of their
election and qualification until their successors have been duly elected and
qualified.

                     A.6(b)(ii)      A vacancy in the directorships to be
elected by the Series Preferred Stockholders pursuant to Section A.6(b)(i), may
be filled only by a vote at a meeting called in accordance with the By-laws of
the Corporation or written consent in lieu of such meeting of (A) in the case of
a vote of such Series Preferred Stockholders at a stockholders' meeting, the
holders of at least a majority in voting power of such Series Preferred Stock or
(B) in the case of written consent in lieu of a meeting, the holders of at least
a majority of the voting power of such Series Preferred Stock.

          A.6(c)     The Corporation shall not, without the affirmative approval
of the holders of shares representing at least sixty five percent (65%) of the
voting power of the Series Preferred Stock then outstanding (determined as set
forth in the second sentence of Section A.6(a) hereof), acting separately from
the holders of Common Stock or any other securities of the Corporation, given by
written consent in lieu of a meeting or by vote at a meeting called for such
purpose, for which meeting or approval by written consent timely and specific
notice (a

                                     - 10 -
<Page>

"Notice") shall have been given to each holder of such Preferred Stock, in the
manner provided in the By-laws of the Corporation:

                     A.6(c)(i)       sell, abandon, transfer, lease, license on
an exclusive basis, or otherwise dispose of all or substantially all of its
properties or assets or make any other sale, transfer, lease or disposition of
its assets other than in the ordinary course of its business;

                     A.6(c)(ii)      purchase, lease or otherwise acquire all or
substantially all of the assets of another entity;

                     A.6(c)(iii)     except as otherwise required by this Sixth
Restated Certificate of Incorporation, declare or pay any dividend or make any
distribution with respect to shares of its capital stock (whether in cash,
shares, capital stock or other securities or property);

                     A.6(c)(iv)      except as otherwise required by this Sixth
Restated Certificate of Incorporation or in any agreement approved by the Board
of Directors with a director, officer, employee, consultant or independent
contractor of or to the Corporation providing for the repurchase of any of its
capital stock owned by such director, officer, employee, consultant or
independent contractor at the option of the Corporation, provided that such
agreements are either:

                                     (A)  set forth on Schedule 5.2 to the
Series F Stock Purchase Agreement, or

                                     (B)  entered into pursuant to the 1993
Equity Incentive Plan of the Corporation, as amended with requisite Board and
Stockholder approvals from time to time, (the "1993 Equity Incentive Plan") or
any stock option plan which has been adopted by the Corporation and approved by
the Board of Directors and by the holders of at least a majority of the combined
voting power of the Series Preferred Stock then outstanding (including any
outstanding shares of Common Stock issued upon conversion thereof), and the form
of option agreement under the Equity Incentive Plan is satisfactory in form and
in substance, except for immaterial changes thereto may from time to time by
officers of the Corporation, to the Board of Directors and to the holders of at
least a majority of the combined voting power of the Series Preferred Stock then
outstanding (including any outstanding shares of Common Stock issued upon
conversion thereof),

make any payment on account of the purchase, redemption or other retirement of
any share of capital stock of the Corporation, or distribute to Common
Stockholders shares of the Corporation's capital stock (other than Common Stock)
or other securities of other entities, evidences of indebtedness issued by the
Corporation or other entities, or other assets or options or rights (excluding
options to purchase and rights to subscribe for shares of Common Stock or the
securities of the Corporation convertible into or exchangeable for shares of
Common Stock);

                     A.6(c)(v)       merge or consolidate with or into, or
permit any subsidiary to merge or consolidate with or into, any other
corporation, corporations or other entity or entities;

                                     - 11 -
<Page>

                     A.6(c)(vi)      voluntarily dissolve, liquidate or wind-up
or carry out any partial liquidation or distribution or transaction in the
nature of a partial liquidation or distribution;

                     A.6(c)(vii)     in any manner alter or change the
designations, powers, preferences, rights, qualifications, limitations or
restrictions of the Series Preferred Stock;

                     A.6(c)(viii)    take any action to cause any amendment,
alteration or repeal of any of the provisions of this Sixth Restated Certificate
of Incorporation or the By-laws of the Corporation;

                     A.6(c)(ix)      except for the issuance of capital stock or
other securities constituting shares of Excluded Stock (as defined in Section
A.7(d)(iii) below), authorize, designate, create, issue or agree to issue any
equity or debt security of the Corporation or any security right, option or
warrant convertible into, or exercisable or exchangeable for, shares of the
capital stock of the Corporation or any capitalized lease with an equity feature
with respect to the capital stock of the Corporation;

                     A.6(c)(x)       amend, modify or terminate the 1993 Equity
Incentive Plan of the Corporation or amend or modify any stock option agreement
or restricted stock purchase agreement entered into between the Corporation and
its employees, directors or consultants, except for immaterial changes made
thereto from time to time by officer of the Corporation; or

                     A.6(c)(xi)      accelerate the vesting schedule or exercise
date or dates of any such options or in any stock option agreement entered into
between the Corporation and its directors, officers, employees, consultants or
independent contractors, or waive or modify the Corporation's repurchase rights
with respect to any shares of the Corporation's stock issuable pursuant to any
restricted stock purchase agreement entered into between the Corporation and its
directors, officers, employees, consultants or independent contractors.

          A.6(d)     The Corporation shall not, without the affirmative approval
of the holders of shares representing at least two-thirds (66 2/3rd %) of the
voting power of the outstanding shares of Series C Stock, voting separately as a
single class:

                     A.6(d)(i)       amend or repeal any provision of, or add
any provision to, this Sixth Restated Certificate of Incorporation if such
action would materially and adversely alter or change the preferences, rights,
privileges, or powers of, or the restrictions provided for the benefit of, the
Series C Stock;

                     A.6(d)(ii)      increase or decrease the number of
authorized shares of Series C Stock;

                     A.6(d)(iii)     authorize, create, or issue shares of any
class or series of Preferred Stock or stock either (A) on a parity with, or (B)
having any preference or priority as to, the Series C Stock with respect to
dividends or redemption rights, liquidation preferences, conversion rights, or
voting rights.

                                     - 12 -
<Page>

          A.6(e)     The Corporation shall not, without the affirmative approval
of the holders of shares representing at least two-thirds (66 2/3rd %) of the
voting power of the outstanding shares of Series D Stock, voting separately as a
single class:

                     A.6(e)(i)       amend or repeal any provision of, or add
any provision to, this Sixth Restated Certificate of Incorporation if such
action would materially and adversely alter or change the preferences, rights,
privileges, or powers of, or the restrictions provided for the benefit of, the
Series D Stock;

                     A.6(e)(ii)      authorize, create, or issue shares of any
class or series of Preferred Stock or stock having any preference or priority as
to the Series D Stock with respect to dividends or redemption rights,
liquidation preferences, conversion rights, or voting rights.

          A.6(f)     The Corporation shall not, without the affirmative approval
of the holders of shares representing at least sixty five percent (65%) of the
voting power of the outstanding shares of Series E Stock, voting separately as a
single class:

                     A.6(f)(i)       amend or repeal any provision of, or add
any provision to, this Sixth Restated Certificate of Incorporation if such
action would materially and adversely alter or change the preferences, rights,
privileges, or powers of, or the restrictions provided for the benefit of, the
Series E Stock;

                     A.6(f)(ii)      increase or decrease the number of
authorized shares of Series E Stock;

                     A.6(f)(iii)     authorize, create, or issue shares of any
class or series of Preferred Stock or stock having any preference or priority as
to the Series E Stock with respect to dividends or redemption rights,
liquidation preferences, conversion rights, or voting rights.

     A.7  CONVERSION.

          A.7(a)(i)  Any Series Preferred Stockholder shall have the right, at
any time or from time to time, to convert any or all of its Series Preferred
Stock into that number of fully paid and nonassessable shares of Common Stock
for each share of Series Preferred Stock so converted equal to the quotient of
the Original Purchase Price for such share divided by the Conversion Price for
such share (as defined in Section A.7(d) hereof), as last adjusted and then in
effect, rounded up to the nearest one-tenth of a share; PROVIDED, HOWEVER, that
cash shall be paid in lieu of the issuance of fractional shares of Common Stock,
as provided in Section A.7(c)(ii) hereof.

                     A.7(a)(ii)      Any Series Preferred Stockholder who
exercises the right to convert shares of Series Preferred Stock into shares of
Common Stock, pursuant to this Section A.7, shall be entitled to conversion into
Common Stock, in accordance with the provisions of this Section A.7 of all
accrued or declared but unpaid dividends payable with respect to such Series
Preferred Stock pursuant to Section A.3(a) and/or A.3(b) herein, as the case may
be, up to and including the Conversion Date (as defined in Section A.7(b)(ii)
hereof); PROVIDED THAT, the Conversion Price for such purposes shall be the then
fair market value of the Common Stock as determined by the Board of Directors of
the Corporation.

                                     - 13 -
<Page>

          A.7(b)(i)  Any Series Preferred Stockholder may exercise the right
to convert such shares into Common Stock pursuant to this Section A.7 by
delivering to the Corporation during regular business hours, at the office of
the Corporation or any transfer agent of the Corporation or at such other place
as may be designated by the Corporation, the certificate or certificates for the
shares to be converted (solely for purposes of this Section A.7, the "Series
Preferred Certificate"), duly endorsed or assigned in blank to the Corporation
(if required by it).

                     A.7(b)(ii)      Each Series Preferred Certificate shall be
accompanied by written notice stating that such holder elects to convert such
shares and stating the name or names (with address) in which the certificate or
certificates for the shares of Common Stock (the "Common Certificate") are to be
issued. Such conversion shall be deemed to have been effected on the date when
such delivery is made, and such date is referred to herein as the "Conversion
Date."

                     A.7(b)(iii)     As promptly as practicable thereafter, the
Corporation shall issue and deliver to or upon the written order of such holder,
at the place designated by such holder, a certificate or certificates for the
number of full shares of Common Stock to which such holder is entitled and a
check or cash in respect of any fractional interest in any shares of Common
Stock, as provided in Section A.7(c)(ii) hereof, payable with respect to the
shares so converted up to and including the Conversion Date.

                     A.7(b)(iv)      The person in whose name the certificate or
certificates for Common Stock are to be issued shall be deemed to have become a
holder of record of Common Stock on the applicable Conversion Date, unless the
transfer books of the Corporation are closed on such Conversion Date, in which
event the holder shall be deemed to have become the stockholder of record on the
next succeeding date on which the transfer books are open, provided that the
Conversion Price shall be that Conversion Price in effect on the Conversion
Date.

                     A.7(b)(v)       Upon conversion of only a portion of the
number of shares covered by a Series Preferred Certificate, the Corporation
shall issue and deliver to or upon the written order of the holder of such
Series Preferred Certificate, at the expense of the Corporation, a new
certificate covering the number of shares of the Series Preferred Stock
representing the unconverted portion of the Series Preferred Certificate, which
new certificate shall entitle the holder thereof to all the rights, powers and
privileges of a holder of such shares.

          A.7(c)(i)  If a Series Preferred Stockholder shall surrender more than
one share of Series Preferred Stock for conversion at any one time, then the
number of full shares of Common Stock issuable upon conversion thereof shall be
computed on the basis of the aggregate number of shares of Series Preferred
Stock so surrendered.

                     A.7(c)(ii)      No fractional shares of Common Stock shall
be issued upon conversion of Series Preferred Stock. The Corporation shall pay a
cash adjustment for any such fractional interest in an amount equal to the
Current Market Price thereof on the Conversion Date, as determined in accordance
with Section A.7(d)(ix) hereof.

          A.7(d)     The conversion price at which shares of Common Stock shall
be issued upon conversion of the Series A Stock without the payment of
additional consideration by the

                                     - 14 -
<Page>

holder thereof shall initially be equal to $8.00 per share, after giving effect
to the Corporation's one-for-eight (1:8) reverse stock split of the Common Stock
which was effected on April 4, 1997 (the "Reverse Stock Split") (the "Series A
Conversion Price"). The conversion price at which shares of Common Stock shall
be issued upon conversion of Series B Stock without the payment of additional
consideration by the holder thereof shall initially be equal to $4.00 per share,
after giving effect to the Reverse Stock Split (the "Series B Conversion
Price"). The conversion price at which shares of Common Stock shall be issued
upon conversion of Series C Stock without the payment of additional
consideration by the holder thereof shall initially be equal to $3.80 per share
(the "Series C Conversion Price"). The conversion price at which shares of
Common Stock shall be issued upon conversion of Series D Stock without the
payment of additional consideration by the holder thereof shall initially be
equal to $7.2037 per share (the "Series D Conversion Price"). The conversion
price at which shares of Common Stock shall be issued upon conversion of Series
E Stock without the payment of additional consideration by the holder thereof
shall initially be equal to $7.2037 per share (the "Series E Conversion Price").
The conversion price at which shares of Common Stock shall be issued upon
conversion of Series F Junior Stock without the payment of additional
consideration by the holder thereof shall initially be equal to $14.00 per share
(the "Series F Conversion Price"). The Series A Conversion Price, the Series B
Conversion Price, the Series C Conversion Price, the Series D Conversion Price,
the Series E Conversion Price and the Series F Conversion Price are referred to
collectively herein as the "Conversion Price." Such Conversion Price, and the
rate at which shares of Series Preferred Stock may be converted into shares of
Common Stock, shall be subject to adjustment from time to time as follows:

                     A.7(d)(i)(A)    Subject to Section A.7(d)(iii) below, if
the Corporation shall, at any time or from time to time after the Original
Issuance Date of the Series E Stock issue any shares of Common Stock (which
term, for purposes of this Section A.7(d)(i)(A) and Section A.7(d)(iii),
including all subsections thereof, shall be deemed to include all other
securities convertible into, or exchangeable or exercisable for, shares of
Common Stock (including, but not limited to, Series Preferred Stock)) or options
to purchase or other rights to subscribe for such convertible or exchangeable
securities, in each case other than Excluded Stock (as defined in Section
A.7(d)(iv) below), for a consideration per share less than the Series E
Conversion Price in effect immediately prior to the issuance of such Common
Stock or other securities (a "Series E Dilutive Issuance"), the Series E
Conversion Price for the Series E Stock in effect immediately prior to each such
Series E Dilutive Issuance shall automatically be lowered to an amount per share
(the "Series E Price Per Share") equal to the consideration per share received
by the Corporation for the issue of the shares of Common Stock; PROVIDED,
HOWEVER, that with respect to any Series E Stock held by a person or entity that
is an Investor, as such term is defined in Section A.7(d)(iii)(A) below, the
Series E Conversion Price in effect immediately prior to each such Series E
Dilutive Issuance shall be subject to adjustment as provided in Section
A.7(d)(iii) below, subject to Section A.7(d)(iii)(G).

                                     A.7(d)(i)(B)   Subject to Section
A.7(d)(iii) below, if the Corporation shall, at any time or from time to time
after the Original Issuance Date of the Series B Stock, the Series C Stock, the
Series D Stock or the Series F Junior Stock, as the case may be, issue any
shares of Common Stock (which term, for purposes of this Section A.7(d)(i)(B)
and Section A.7(d)(iii), including all subsections thereof, shall be deemed to
include all other securities convertible into, or exchangeable or exercisable
for, shares of Common Stock

                                     - 15 -
<Page>

(including, but not limited to, Series Preferred Stock)) or options to purchase
or other rights to subscribe for such convertible or exchangeable securities, in
each case other than Excluded Stock, for a consideration per share less than the
applicable Conversion Price in effect immediately prior to the issuance of such
Common Stock or other securities (a "Junior Series Preferred Dilutive Issuance"
and, together with any Series E Dilutive Issuance, a "Dilutive Issuance"), the
Series B Conversion Price, and/or the Series C Conversion Price, and/or the
Series D Conversion Price, and/or Series F Conversion Price, as applicable, for
the Series B Stock, and/or Series C Stock, and/or Series D Stock, and/or the
Series F Junior Stock in effect immediately prior to each such Junior Series
Preferred Dilutive Issuance shall automatically be lowered to an amount per
share (the "Junior Series Preferred Price Per Share") determined by multiplying
the previously applicable Conversion Price by a fraction, (A) the numerator of
which shall be (1) the number of shares of Common Stock outstanding immediately
prior to such issue plus (2) the number of shares of Common Stock which the
aggregate consideration received or to be received by the Corporation for the
total number of additional shares of Common Stock so issued would purchase at
such Conversion Price; and (B) the denominator of which shall be the number of
shares of Common Stock outstanding immediately prior to such issue plus the
number of such additional shares of Common Stock so issued; PROVIDED THAT, (i)
for the purpose of this Subsection A.7(d)(i)(B), all shares of Common Stock
issuable upon exercise or conversion of options or convertible securities
outstanding immediately prior to such issue shall be deemed to be outstanding,
and (ii) the number of shares of Common Stock deemed issuable upon exercise or
conversion of such outstanding options and convertible securities shall not give
effect to any adjustments to the conversion price or conversion rate of such
options or convertible securities resulting from the issuance of additional
shares of Common Stock that is the subject of this calculation; PROVIDED,
HOWEVER, that with respect to any Series A, B, C and D Preferred Stock held by a
person or entity that is an Investor, as such term is defined in Section
A.7(d)(iii)(A) below, the Conversion Price in effect immediately prior to each
such Junior Dilutive Issuance shall be subject to adjustment as provided in
Section A.7(d)(iii) below, subject to Section A.7(d)(iii)(G).

          A.7(d)(ii) For the purposes of any adjustment of the Conversion
Price pursuant to Section A.7(d)(i) and Section A.7(d)(iii) the following
provisions shall be applicable:

                     A.7(d)(ii)(A) In the case of the issuance of Common Stock
in whole or in part for cash, the consideration shall be deemed to be the amount
of cash paid therefor after deducting therefrom any discounts, commissions or
other expenses allowed, paid or incurred by the Corporation for any underwriting
or otherwise in connection with the issuance and sale thereof, plus the value of
any property other than cash received by the Corporation, determined as provided
in Section A.7(d)(ii)(B) hereof, plus the value of any other consideration
received by the Corporation determined as set forth in Section A.7(d)(ii)(C)
hereof.

                     A.7(d)(ii)(B) In the case of the issuance of Common Stock
for a consideration in whole or in part in property other than cash, the value
of such property other than cash shall be deemed to be the fair market value of
such property as determined in good faith by the Board of Directors,
irrespective of any accounting treatment; PROVIDED, HOWEVER, that such fair
market value of such property as determined by the Board of Directors shall not
exceed the aggregate Current Market Price (as defined in Section A.7(d)(ix)
hereof) of the shares of Common Stock being issued, less any cash consideration
paid for such shares, determined as

                                     - 16 -
<Page>

provided in Section A.7(d)(ii)(A) hereof and less any other consideration
received by the Corporation for such shares, determined as set forth in Section
A.7(d)(ii)(C) hereof.

                     A.7(d)(ii)(C) In the case of the issuance of Common Stock
for consideration in whole or in part other than cash or property, the value of
such other consideration shall be deemed to be the aggregate par value of such
Common Stock (or the aggregate stated value if such Common Stock has no par
value).

                     A.7(d)(ii)(D) In the case of the issuance of options or
other rights to purchase or subscribe for Common Stock, securities by their
terms convertible into or exchangeable for Common Stock or options to purchase
or other rights to subscribe for such convertible or exchangeable securities:

                                     A.7(d)(ii)(D)(1)   the aggregate maximum
number of shares of Common Stock deliverable upon exercise of such options to
purchase or rights to subscribe for Common Stock shall be deemed to have been
issued at the time such options or rights were issued and for a consideration
equal to the consideration (determined in the manner provided in Sections
A.7(d)(ii)(A), (B) and (C) hereof), if any, received by the Corporation upon the
issuance of such options or rights plus the minimum purchase price provided in
such options or rights for the Common Stock covered thereby (the consideration
in each case to be determined in the manner provided in Sections A.7(d)(ii)(A),
(B) and (C) hereof);

                                     A.7(d)(ii)(D)(2)   the aggregate maximum
number of shares of Common Stock deliverable upon conversion of, or in exchange
for, any such convertible or exchangeable securities or upon the exercise of
options to purchase or rights to subscribe for such convertible or exchangeable
securities and subsequent conversion or exchange thereof shall be deemed to have
been issued at the time such securities were issued or such options or rights
were issued and for a consideration equal to the consideration received by the
Corporation for any such securities and related options or rights (excluding any
cash received on account of accrued interest or accrued dividends), plus the
minimum additional consideration, if any, to be received by the Corporation upon
the conversion or exchange of such securities or the exercise of any related
options or rights (the consideration in each case to be determined in the manner
provided in Sections A.7(d)(ii)(A), (B) and (C) hereof);

                                     A.7(d)(ii)(D)(3)   if there is any change
in the exercise price of, or number of shares deliverable upon exercise of, any
such options or rights or upon the conversion or exchange of any such
convertible or exchangeable securities (other than a change resulting from the
antidilution provisions thereof), then the Conversion Price shall automatically
be readjusted in proportion to such change; and

                                     A.7(d)(ii)(D)(4)   upon the expiration of
any such options or rights or the termination of any such rights to convert or
exchange such convertible or exchangeable securities, the Conversion Price shall
be automatically readjusted to the Conversion Price that would have obtained had
such options, rights or convertible or exchangeable securities not been issued.

                                     - 17 -
<Page>

          A.7(d)(iii)  With respect to any Dilutive Issuance (other than with
respect to the Series F Junior Stock, it being understood that the provisions of
this Section A.7(d)(iii) shall not be applicable to the holders of Series F
Junior Stock):

                       A.7(d)(iii)(A)     If: (1) a holder of Series Preferred
Stock that is a signatory to the Stockholders' Agreement (such holder, an
"Investor") has purchased, in every Dilutive Issuance subsequent to the date
that such Investor first became an "Investor" under the Stockholders' Agreement
(the "Investor Date") other than in Exempt Transactions (as defined in
subsection A.7(d)(iii)(E) below), no less than such Investor's then-current
percentage ownership of all outstanding Common Stock determined on a fully
diluted basis immediately prior to each Dilutive Issuance (I.E., assuming the
conversion of all convertible securities, the exercise of all warrants, options
or other rights and the exchange of all exchangeable securities) (as to each
Investor, the "Ownership Percentage") pursuant to the exercise of such
Investor's right of first refusal (the "Right of First Refusal") set forth in
the Stockholders' Agreement (each such Investor, a "Fully Participating
Investor"), or (2) an Investor has received its shares of Series Preferred Stock
as a result of an original issuance from the Corporation and such Investor has
never had the opportunity to exercise its Right of First Refusal, in whole or in
part (a "New Investor"), or (3) a particular Dilutive Issuance is an Exempt
Transaction; then, provided that such Fully Participating Investor or New
Investor purchases at least its Ownership Percentage of Common Stock in the
then-current Dilutive Issuance (unless such Dilutive Issuance is an Exempt
Transaction), the Conversion Price in effect immediately prior to such Dilutive
Issuance or Exempt Transaction, as the case may be, for the Series Preferred
Stock held by such Fully Participating Investor or such New Investor, including
any Series Preferred Stock issued in the Dilutive Issuance or the Exempt
Transaction, automatically shall be adjusted in accordance with Section
A.7(d)(i)(A) with respect to the Series E Stock, or Section A.7(d)(i)(B) with
respect to the Series A Stock, the Series B Stock, the Series C Stock or the
Series D Stock.

                       A.7(d)(iii)(B)     Except in the case of an Exempt
Transaction, in the event that an Investor does not purchase any shares of
Common Stock pursuant to its Right of First Refusal, there shall be no
adjustment to the Conversion Price of the shares of Series Preferred Stock held
by such Investor as a result of such Dilutive Issuance.

                       A.7(d)(iii)(C)     In any instance when an Investor
purchases a number of shares of Common Stock that is less than such Investor's
Ownership Percentage of the Common Stock offered in such Dilutive Issuance, then
the Conversion Price in effect immediately prior to such Dilutive Issuance (the
"Investor Conversion Price") for the Series Preferred Stock held by such
Investor, and the Conversion Price for the Series Preferred Stock issued in the
then-current Dilutive Issuance, shall automatically be lowered by an amount
equal to the product of the difference between the Investor Conversion Price and
(1) the Series E Price Per Share, in the case of an Investor who is a Series E
Stockholder, and (2) the Junior Series Preferred Price Per Share, in the case of
an Investor who is a Series A, B, C & D Preferred Stockholder, multiplied in
each case by the Adjustment Factor (as such term is hereinafter defined).

                                          A.7(d)(iii)(C)(1)  The "Adjustment
Factor" shall be a number equal to the product of the Right of First Refusal
Factor (as such term is hereinafter

                                     - 18 -
<Page>

defined) multiplied by the Dilutive Issuance Purchase Factor (as such term is
hereinafter defined).

                                          A.7(d)(iii)(C)(2)  The "Right of
First Refusal Factor" shall equal the quotient of: (a) the aggregate number of
shares of Common Stock (determined on a fully diluted basis) that such Investor
purchased pursuant to its Right of First Refusal in each Dilutive Issuance that
has occurred since the Investor Date and prior to the then current Dilutive
Issuance, divided by (b) the aggregate number of shares of Common Stock
(determined on a fully diluted basis) that such Investor was entitled to
purchase in each such Dilutive Issuance (other than the then-current Dilutive
Issuance) pursuant to its Right of First Refusal since the Investor Date had
such Investor purchased its full Ownership Percentage of such Common Stock
offered in all Dilutive Issuances other than Exempt Transactions
(notwithstanding the foregoing, in no event shall the Right of First Refusal
Factor exceed 1.00).

                                          A.7(d)(iii)(C)(3)  The "Dilutive
Issuance Purchase Factor" shall equal the total number of shares of Common Stock
purchased by the Investor in the then current Dilutive Issuance divided by the
product of such Investor's Ownership Percentage multiplied by the number of
shares of Common Stock issued by the Corporation in such Dilutive Issuance.

                       A.7(d)(iii)(D)     In the case of: (1) an Investor which
is not a Fully Participating Investor which exercises its Right of First Refusal
to purchase at least its Ownership Percentage of the Offered Securities in a
Dilutive Issuance, or (2) an Exempt Transaction (and solely with respect to any
Investor which is not a Fully Participating Investor or a New Investor), then
the Conversion Price then in effect for the shares of Series Preferred Stock
held by such Investor, including any shares of Series Preferred Stock issued to
an Investor under the circumstances described in the foregoing subsections (1)
or (2), shall be reduced automatically as a result of such Dilutive Issuance or
Exempt Transaction, as the case may be, by an amount equal to the product of the
difference between the Investor Conversion Price and (x) the Series E Price Per
Share, in the case of an Investor who is a Series E Stockholder, and (y) the
Junior Series Preferred Price Per Share, in the case of an Investor who is a
Series A, B, C & D Preferred Stockholder, multiplied in each case by the Right
of First Refusal Factor.

                       A.7(d)(iii)(E)     As used in this Section A.7(d)(iii),
an "Exempt Transaction" is any Dilutive Issuance with respect to which either
(1) all Investors waive their Rights of First Refusal and elect not to purchase
any of the Common Stock offered with respect to such Dilutive Issuance, or (2)
notwithstanding anything to the contrary set forth in this Section A.7(d)(iii),
Investors holding a majority of the shares of Common Stock held by all Investors
(determined on a fully diluted basis) make a written election to treat such
Dilutive Issuance as an Exempt Transaction.

                       A.7(d)(iii)(F)     In the event that an Investor
transfers any shares of Series Preferred Stock (the "Transferred Stock") to any
third party, no adjustment to the Conversion Price of such Transferred Stock
shall be made as a result of such transfer.

                       A.7(d)(iii)(G)     Upon the written election of 75% of
the combined voting power of the Series A, B, C & D Preferred Stock then
outstanding, calculated in

                                     - 19 -
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accordance with Section A.6(a) above, the provisions of this Section A.7(d)(iii)
shall not be applicable to any particular Series A, B, C & D Preferred Dilutive
Issuance. Upon the written election of 75% of the voting power of the Series E
Preferred Stock then outstanding, calculated in accordance with Section A.6(a)
above, the provisions of this Section A.7(d)(iii) shall not be applicable to any
particular Series E Dilutive Issuance.

          A.7(d)(iv)   "Excluded Stock" shall mean:

                       A.7(d)(iv)(A)      Shares of Common Stock issued upon
conversion of any shares of Series Preferred Stock;

                       A.7(d)(iv)(B)      Common Stock issued or issuable to
officers, directors or employees of or consultants or independent contractors to
the Corporation, pursuant to any written agreement, plan or arrangement,
including pursuant to any option granted under the 1993 Equity Incentive Plan,
as amended, to purchase, or rights to subscribe for, such Common Stock, that is
set forth on Schedule 5.2 to the Series F Stock Purchase Agreement or that has
been approved in form and substance by the holders of at least a majority of the
combined voting power of the Series Preferred Stock then outstanding (determined
in accordance with Section A.6(a) hereof and including in such calculation any
shares of Series Preferred Stock which have been converted by the holder thereof
into shares of the Corporation's Common Stock), and which, as a condition
precedent to the issuance of such shares, provides for the vesting of such
shares and subjects such shares to restrictions on transfers and rights of first
offer or refusal in favor of the Corporation on terms that have been approved by
the holders of at least a majority of the combined voting power of the Series
Preferred Stock then outstanding (determined in accordance with Section A.6(a)
hereof and including in such calculation any shares of Series Preferred Stock
which have been converted by the holder thereof into Shares of the Corporation's
Common Stock) (collectively, the "Required Terms"), unless any of such Required
Terms are waived by holders of shares representing at least a majority of the
voting power of the Series Preferred Stock then outstanding (determined as set
forth in Section A.6(a) hereof);

                       A.7(d)(iv)(C)      Common Stock issued as a stock
dividend payable in shares of Common Stock, or capital stock of any class
issuable upon any subdivision, recombination, split-up or reverse stock split of
all the outstanding shares of such class of capital stock;

                       A.7(d)(iv)(D)      A maximum of 516,364 shares of Common
Stock (subject to adjustment) issued or issuable upon exercise of Common Stock
Purchase Warrants issued:

     (1)  pursuant to the terms of any one of the following Credit Agreements by
and between the Corporation and the Lenders defined therein;

          (a)   Credit Agreement dated July 27, 1994;

          (b)   Credit Agreement dated December 20, 1994;

          (c)   Credit Agreement dated June 20, 1995;

                                     - 20 -
<Page>

          (d)   One or more Credit Agreements dated on or after January 10,
1996 and on or before June 30, 1996; and

          (e)   One or more Credit Agreements dated on or after September 30,
1996 and on or before February 28, 1997; or

     (2)  on or after July 2, 1994 to certain investors of the Corporation in
connection with the issuance by such investors to the Corporation's auditors of
letters in which such investors commit to provide capital support to the
Corporation through December 31, 1994;

                       A.7(d)(iv)(E)      12,500 shares of Common Stock (subject
to adjustment) issued to Dominion Fund III pursuant to that certain Common Stock
Purchase Agreement by and among the Corporation and Dominion Fund III dated July
27, 1994;

                       A.7(d)(iv)(F)      the Series B Stock Purchase Warrants
to purchase an aggregate of 495,000 shares of Series B Preferred Stock issued on
April 11, 1996, September 30, 1996 and April 7, 1997 to Trustees of Boston
University (the "BU Warrants"), a maximum of 495,000 shares of Series B Stock
issued or issuable upon the exercise of the BU Warrants and the shares of Common
Stock issued or issuable upon conversion of the Series B Stock issued upon
exercise of the BU Warrants;

                       A.7(d)(iv)(G)      Shares of Series B Preferred Stock
issued by the Corporation on or after June 30, 1995 pursuant to (i) the Series B
Convertible Preferred Stock Purchase Agreement dated June 20, 1995 by and among
the Corporation and the persons named on Schedule I thereto; and (ii) the Series
B Convertible Preferred Stock Purchase Agreement dated April 4, 1997 by and
among the Corporation and the persons named on Schedule thereto;

                       A.7(d)(iv)(H)      Common Stock or other securities
issued in connection with equipment leasing or equipment financing arrangements,
up to a maximum number of shares of Common Stock or other securities equal to 5%
of the outstanding capital stock (counting all convertible Preferred Stock on an
as-converted basis) of the Corporation;

                       A.7(d)(iv)(I)      Common Stock or other securities
issued in connection with the acquisition or licensing-in of technology, which
issuances are not undertaken primarily for the purpose of raising capital, up to
a maximum number of shares of Common Stock or other securities equal to 5% of
the outstanding capital stock (counting all convertible Preferred Stock on an
as-converted basis) of the Corporation;

                       A.7(d)(iv)(J)      Common Stock or other securities
issued in connection with a research, development and/or commercialization
agreement or arrangement between the Corporation and a pharmaceutical,
biopharmaceutical, biotechnology or similar entity in which equity securities of
the Corporation are sold to such entity or an affiliate of such entity for cash
consideration, up to a maximum number of shares of Common Stock or other
securities equal to 5% of the outstanding capital stock (counting all
convertible Preferred Stock on an as-converted basis) of the Corporation.

          A.7(d)(v)    If the number of shares of Common Stock outstanding at
any time after the Original Issuance Date (as hereinafter defined) is increased
by a stock dividend payable

                                     - 21 -
<Page>

in shares of Common Stock or by a subdivision or split-up of shares of Common
Stock, then, following the record date fixed for the determination of holders of
Common Stock entitled to receive such stock dividend, subdivision or split-up,
the Conversion Price shall be appropriately decreased so that the number of
shares of Common Stock issuable on conversion of each share of Series Preferred
Stock shall be increased in proportion to such increase in outstanding shares.

          A.7(d)(vi)   If, at any time after the date of filing of this Sixth
Restated Certificate of Incorporation, the number of shares of Common Stock
outstanding is decreased by a combination of the outstanding shares of Common
Stock, then, following the record date for such combination, the Conversion
Price shall be appropriately increased so that the number of shares of Common
Stock issuable on conversion of each share of Series Preferred Stock shall be
decreased in proportion to such decrease in outstanding shares.

          A.7(d)(vii)  In the event, at any time after the Original Issuance
Date, of any capital reorganization, or any reclassification of the capital
stock of the Corporation (other than a change in par value or from par value to
no par value or from no par value to par value or as a result of a stock
dividend or subdivision, split-up or combination of shares), or the
consolidation or merger of the Corporation with or into another person (other
than consolidation or merger in which the Corporation is the continuing
corporation and which does not result in any change in the powers, designations,
preferences and rights, or the qualifications, limitations or restrictions, if
any, of the capital stock of the Corporation) or of the sale or other
disposition of all or substantially all the properties and assets of the
Corporation as an entirety to any other person (any such transaction, an
"Extraordinary Transaction"), then the Corporation shall provide appropriate
adjustment to the Conversion Price with respect to each share of Series
Preferred Stock outstanding after the effectiveness of such Extraordinary
Transaction (and excluding any Series Preferred Stock redeemed pursuant to
Section A.4(j) hereof in connection therewith) such that each share of Series
Preferred Stock outstanding immediately prior to the effectiveness of the
Extraordinary Transaction (other than the shares redeemed pursuant to Section
A.4(j) hereof) shall be convertible into the kind and number of shares of stock
or other securities or property of the Corporation, or of the corporation
resulting from or surviving such Extraordinary Transaction, that a holder of the
number of shares of Common Stock deliverable (immediately prior to the
effectiveness of the Extraordinary Transaction) upon conversion of such share of
Series Preferred Stock would have been entitled to receive upon such
Extraordinary Transaction. The provisions of this Section A.7(d)(vii) shall
similarly apply to successive Extraordinary Transactions.

          A.7(d)(viii) All calculations under this Section A.7(d) shall be made
to the nearest one-tenth of a cent ($.001) or to the nearest one-tenth of a
share, as the case may be.

          A.7(d)(ix)   For the purpose of any computation pursuant to Section
A.7(c) hereof or this Section A.7(d), the Current Market Price at any date of
one share of Common Stock shall be deemed to be the average of the daily closing
prices for the 30 consecutive business days ending on the fifth (5th) business
day before the day in question (as adjusted for any stock dividend, split-up,
combination or reclassification that took effect during such 30-business day
period) as follows:

                                     - 22 -
<Page>

                       A.7(d)(ix)(A)      If the Common Stock is listed or
admitted for trading on a national securities exchange, then the closing price
for each day shall be the last reported sales price regular way or, in case no
such reported sales took place on such day, the average of the last reported bid
and asked prices regular way, in either case on the principal national
securities exchange on which the Common Stock is listed or admitted to trading.

                       A.7(d)(ix)(B)      If the Common Stock is not at the time
listed or admitted for trading on any such exchange, then such price as shall be
equal to the last reported sale price, or if there is no such sale price, the
average of the last reported bid and asked prices, as reported by the Nasdaq
Stock Market ("Nasdaq") on such day.

                       A.7(d)(ix)(C)      If the Common Stock is not at the time
quoted on the Nasdaq, then such price shall be equal to the last reported bid
and asked prices on such day as reported by the National Quotation Bureau, Inc.,
or any similar reputable quotation and reporting service, if such quotation is
not reported by the National Quotation Bureau, Inc.

                       A.7(d)(ix)(D)      If the Common Stock is not traded in
such manner that the quotations referred to in this Section A.7(d)(ix) are
available for the period required hereunder, then the Current Market Price shall
be the fair market value of such share, as determined in good faith by a
majority of the entire Board of Directors.

          A.7(d)(x)    In any case in which the provisions of this
Section A.7(d) shall require that an adjustment shall become effective
immediately after a record date for an event, the Corporation may defer until
the occurrence of such event (A) issuing to the holder of any share of Series
Preferred Stock converted after such record date and before the occurrence of
such event the additional shares of capital stock issuable upon such conversion
by reason of the adjustment required by such event over and above the shares of
capital stock issuable upon such conversion before giving effect to such
adjustment, and (B) paying to such holder any cash amounts in lieu of fractional
shares pursuant to Section A.7(c)(ii) hereof; PROVIDED, HOWEVER, that the
Corporation shall deliver to such holder a due bill or other appropriate
instrument evidencing such holder's right to receive such additional shares, and
such cash, upon the occurrence of the event requiring such adjustment.

          A.7(d)(xi)   If a state of facts shall occur that, without being
specifically controlled by the provisions of this Section A.7, would not fairly
protect the conversion rights of the holders of the Series Preferred Stock in
accordance with the essential intent and principles of such provisions, then the
Board of Directors shall make an adjustment in the application of such
provisions, in accordance with such essential intent and principles, so as to
protect such conversion rights.

          A.7(e)   Whenever the Conversion Price shall be adjusted as provided
in Section A.7(d) hereof, the Corporation shall forthwith file and keep on
record at the office of the Secretary of the Corporation and at the office of
the transfer agent for the Series Preferred Stock or at such other place as may
be designated by the Corporation, a statement, signed by its President or Chief
Executive Officer and by its Treasurer or Chief Financial Officer, showing in
detail the facts requiring such adjustment and the Conversion Price that shall
be in effect after such adjustment. The Corporation shall also cause a copy of
such statement to be sent by

                                     - 23 -
<Page>

first-class, certified mail, return receipt requested, postage prepaid, to each
Series Preferred Stockholder at such holder's address appearing on the
Corporation's records. Where appropriate, such copy shall be given in advance of
any such adjustment and shall be included as part of a notice required to be
mailed under the provisions of Section A.7(f) hereof.

          A.7(f)   In the event the Corporation shall propose to take any action
of the types described in Section A.7(d)(i), (iii), (v), (vi) or (vii) hereof,
or any other Event of Sale, the Corporation shall give notice to each Series
Preferred Stockholder in the manner set forth in Section A.7(e) hereof, which
notice shall specify the record date, if any, with respect to any such action
and the date on which such action is to take place. Such notice shall also set
forth such facts with respect thereto as shall be reasonably necessary to
indicate the effect of such action (to the extent such effect may be known at
the date of such notice) on the Conversion Price with respect to the Series
Preferred Stock, and the number, kind or class of shares or other securities or
property which shall be deliverable or purchasable upon each conversion of
Series Preferred Stock. In the case of any action that would require the fixing
of a record date, such notice shall be given at least 20 days prior to the
record date so fixed, and in the case of any other action, such notice shall be
given at least 30 days prior to the taking of such proposed action.

          A.7(g)   The Corporation shall pay all documentary, stamp or other
transactional taxes attributable to the issuance or delivery of shares of
capital stock of the Corporation upon conversion of any shares of Series
Preferred Stock; PROVIDED, HOWEVER, that the Corporation shall not be required
to pay any taxes which may be payable in respect of any transfer involved in the
issuance or delivery of any certificate for such shares in a name other than
that of the Series Preferred Stockholder in respect of which such shares of
Series Preferred Stock are being issued.

          A.7(h)   The Corporation shall reserve out of its authorized but
unissued shares of Common Stock solely for the purpose of effecting the
conversion of the Series Preferred Stock sufficient shares of Common Stock to
provide for the conversion of all outstanding shares of Series Preferred Stock.

          A.7(i)   All shares of Common Stock which may be issued in connection
with the conversion provisions set forth herein will, upon issuance by the
Corporation, be validly issued, fully paid and nonassessable, not subject to any
preemptive or similar rights and free from all taxes, liens or charges with
respect thereto created or imposed by the Corporation.

          A.7(j)   Upon either (1) the consummation of a firm commitment
underwritten public offering of Common Stock of the Corporation registered under
the Securities Act of 1933, pursuant to which (A) Common Stock is offered to the
public at a price of at least $14.4074 per share (subject to adjustment to
reflect stock splits, stock dividends, stock combinations, recapitalizations and
like occurrences), and (B) the net proceeds to the Corporation are at least
$15,000,000, or (2) the written election of the holders of at least sixty six
and two-thirds percent (66 2/3rd %) of the Series Preferred Stock then
outstanding, voting together as one class, each share of Series Preferred Stock
then outstanding shall, by virtue of and immediately prior to the closing of
such firm commitment public offering or at the time specified by such written
election and without any action on the part of the holder thereof, be deemed
automatically converted into that number of shares of Common Stock in which the
Series Preferred Stock would be convertible if such conversion were to occur at
the time of the public offering of Common Stock

                                     - 24 -
<Page>

or at the time specified by such written election. The holder of any shares of
Series Preferred Stock converted into Common Stock pursuant to this Section
A.7(j) shall be entitled to payment of all declared but unpaid dividends, if
any, payable on or with respect to such shares up to and including the date of
the closing of such public offering which shall be deemed the Conversion Date
for purposes of this Section A.7(j). In the event that the price per share at
which Common Stock is offered to the public in a public offering as described
above (the "Public Offering Price Per Share") does not equal at least $14.4074
per share (subject to adjustment to reflect stock splits, stock dividends, stock
combinations, recapitalizations or like occurrences), then each share of Series
E Stock outstanding immediately prior to such public offering shall
automatically be converted into a number of shares of Common Stock equal to the
quotient of $14.4074 (subject to adjustment to reflect stock splits, stock
dividends, stock combinations, recapitalizations or like occurrences) divided by
the Public Offering Price Per Share, rounded up to the nearest one-tenth of a
share. For example, if the Public Offering Price Per Share is $10.00, then each
share of Series E Stock shall, immediately prior to the closing of such public
offering, be deemed automatically converted into 1.4407 shares of Common Stock
($14.4074 DIVIDED BY $10.00 = 1.4407).

     A.8  DEFINITIONS. As used in Section A of this Sixth Restated Certificate
of Incorporation, the following terms shall have the corresponding meanings:

                   "Business Day" shall mean any day other than a Saturday,
Sunday or public holiday in the state where the principal executive office of
the Corporation is located.

                   "Original Issuance Date" shall mean, (i) with respect to the
Series A Stock, December 3, 1993, (ii) with respect to the Series B Stock, June
20, 1995, (iii) with respect to the Series C Stock, December 31, 1997, (iv) with
respect to the Series D Stock, May 17, 1999, (v) with respect to the Series E
Stock, May 22, 2001, and (vi) with respect to the Series F Junior Stock,
November 20, 2001.

                   "Original Purchase Price" shall mean, (i) with respect to the
Series A Stock, $1.00 per share, (ii) with respect to the Series B Stock, $1.00
per share, (iii) with respect to the Series C Stock, $3.80 per share, (iv) with
respect to the Series D Stock, $7.2037 per share, (v) with respect to the Series
E Stock, $7.2037 per share and (vi) with respect to the Series F Junior Stock,
$14.00 per share, in each case subject, for all purposes other than Section A.7
hereof (which provisions shall be applied in accordance with their own terms),
to Proportional Adjustment.

                   "Proportional Adjustment" shall mean an adjustment made to
the price of the Series Preferred Stock upon the occurrence of a stock split,
reverse stock split, stock dividend, stock combination, reclassification or
other similar change with respect to such security, so that the price of one
share of the Series Preferred Stock before the occurrence of any such change
shall equal the aggregate price of the share (or shares or fractional share) of
such security (or any other security) received by the holder of the Series
Preferred Stock with respect thereto upon the effectiveness of such change.

                  PART B. ADDITIONAL SERIES OF PREFERRED STOCK

                                     - 25 -
<Page>

     B.1  DESIGNATION OF ADDITIONAL SERIES OF PREFERRED STOCK. Subject to
Section A.6 hereof, the Board of Directors is hereby expressly authorized to
provide for, designate and issue, out of the authorized but unissued shares of
Preferred Stock, one or more other series of Preferred Stock in addition to the
Series Preferred Stock, subject to the terms and conditions set forth herein.
Before any shares of any such series are issued, the Board of Directors shall
fix, and hereby is expressly empowered to fix, by resolution or resolutions, the
following provisions of the shares of any such series:

                (a)    the designation of such series, the number of shares to
constitute such series and the stated value thereof, if different from the par
value thereof;

                (b)    whether the shares of such series shall have voting
rights or powers, in addition to any voting rights required by law, and, if so,
the terms of such voting rights or powers, which may be full or limited;

                (c)    the dividends, if any, payable on such series, whether
any such dividends shall be cumulative, and, if so, from what dates, the
conditions and dates upon which such dividends shall be payable, the preference
or relation which such dividends shall bear to the dividends payable on any
shares of stock of any other class or series;

                (d)    whether the shares of such class or series shall be
subject to redemption by the Corporation, and, if so, the times, prices and
other conditions of such redemption;

                (e)    the amount or amounts payable with respect to shares of
such class or series upon, and the rights of the holders of such class or series
in, the voluntary or involuntary liquidation, dissolution or winding up, or upon
any distribution of the assets, of the Corporation;

                (f)    whether the shares of such class or series shall be
subject to the operation of a retirement or sinking fund and, if so, the extent
to and manner in which any such retirement or sinking fund shall be applied to
the purchase or redemption of the shares of such class or series for retirement
or other corporate purposes and the terms and provisions relative to the
operation thereof;

                (g)    whether the shares of such class or series shall be
convertible into, or exchangeable for, shares of stock of any other class or
series of any other securities and, if so, the price or prices or the rate or
rates of conversion or exchange and the method, if any, of adjusting the same,
and any other terms and conditions of conversion or exchange;

                (h)    the limitations and restrictions, if any, to be effective
while any shares of such class or series are outstanding upon the payment of
dividends or the making of other distributions on, and upon the purchase,
redemption or other acquisition by the Corporation of, the Common Stock or
shares of stock of any other class or series;

                (i)    the conditions or restrictions, if any, to be effective
while any shares of such class or series are outstanding upon the creation of
indebtedness of the

                                     - 26 -
<Page>

Corporation or upon the issue of any additional stock, including additional
shares of such class or series or of any other class or series; and

                (j)    any other powers, designations, preferences and relative,
participating, optional or other special rights, and any qualifications,
limitations or restrictions thereof.

     The powers, designations, preferences and relative, participating, optional
or other special rights of each series of Preferred Stock, and the
qualifications, limitations or restrictions thereof, if any, may differ from
those of any and all other series at any time outstanding. The Board of
Directors is hereby expressly authorized from time to time to increase (but not
above the total number of authorized shares of Preferred Stock) or decrease (but
not below the number of shares thereof then outstanding) the number of shares of
stock of any series of Preferred Stock (other than the Series Preferred Stock)
which has been designated to one or more series of Preferred Stock pursuant to
this Section B.1.

                              PART C. COMMON STOCK

     C.1  DESIGNATION. The designation of this class of capital stock shall be
"Common Stock," par value $.01 per share ("Common Stock"). The number of shares,
powers, terms, conditions, designations, preferences and privileges, relative,
participating, optional and other special rights, and qualifications,
limitations and restrictions, shall be as set forth in this Part C. The number
of authorized shares of Common Stock may be increased or decreased (but not
below the combined number of shares thereof then outstanding and those reserved
for issuance upon conversion of the Series Preferred Stock) by the affirmative
vote of the holders of the majority of the stock of the Corporation entitled to
vote, irrespective of the provisions of Section 242(b)(2) of the Delaware
General Corporation Law.

     C.2  VOTING. Each Common Stockholder shall be entitled to one vote for each
share of Common Stock held of record on all matters as to which Common
Stockholders shall be entitled to vote, which voting rights shall not be
cumulative.

     C.3  OTHER RIGHTS. Each share of Common Stock issued and outstanding shall
be identical in all respects with each other such share, and no dividends shall
be paid on any shares of Common Stock unless the same dividend is paid on all
shares of Common Stock outstanding at the time of such payment. Except for and
subject to those rights expressly granted to the holders of Preferred Stock and
except as may be provided by the laws of the State of Delaware, the Common
Stockholders shall have all other rights of stockholders, including, without
limitation, (a) the right to receive dividends, when and as declared by the
Board of Directors, out of assets lawfully available therefor, and (b) in the
event of any distribution of assets upon a liquidation, dissolution or
winding-up of the affairs of the Corporation (each, a "Liquidation") or
otherwise, the right to receive ratably and equally, together with the holders
of the Preferred Stock and the holders of outstanding shares of any other class
or series of stock, all the assets and funds of the Corporation remaining after
the payment to the holders of the Preferred Stock of the specific amounts which
they are entitled to receive upon such Liquidation, as provided herein.

                                     - 27 -
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                                   ARTICLE IV

                                REGISTERED AGENT

     The address of the registered office of the Corporation in the State of
Delaware is Corporation Trust Center, 1209 Orange Street, Wilmington, New Castle
County, Delaware 19801. The name of the registered agent of the Corporation at
such address is The Corporation Trust Company.

                                    ARTICLE V

                               BOARD OF DIRECTORS

     Subject to the provisions of Section A.6(c) of Article III hereof, the
number of directors of the Board of Directors shall be not in excess of seven
(7) persons, five (5) of whom shall be Preferred Directors, as defined in
Section A.6(b)(i) of Article III hereof. Unless and except to the extent that
the By-laws of the Corporation otherwise require, the election of directors of
the Corporation need not be by written ballot.

                                   ARTICLE VI

                                     BY-LAWS

     In furtherance and not in limitation of the powers conferred by the laws of
the State of Delaware, the Board of Directors is expressly authorized to adopt,
amend or repeal the By-laws of the Corporation, subject to the provisions of
Section A.6 of Article III hereof.

                                   ARTICLE VII

                               PERPETUAL EXISTENCE

     The Corporation is to have perpetual existence.

                                  ARTICLE VIII

                              AMENDMENTS AND REPEAL

     Except as otherwise specifically provided in this Sixth Restated
Certificate of Incorporation, the Corporation reserves the right at any time,
and from time to time, to amend, alter, change or repeal any provision contained
in this Sixth Restated Certificate of Incorporation, and to add or insert other
provisions authorized at such time by the laws of the State of Delaware, in the
manner now or hereafter prescribed by law; and all rights, preferences and
privileges of whatsoever nature conferred upon stockholders, directors or any
other persons whomsoever by and pursuant to this Sixth Restated Certificate of
Incorporation in its present form or as hereafter amended are granted subject to
the rights reserved in this Article VIII.

                                     - 28 -
<Page>

                                   ARTICLE IX

                          COMPROMISES AND ARRANGEMENTS

     Whenever a compromise or arrangement is proposed between the Corporation
and its creditors or any class of them and/or between the Corporation and its
stockholders or any class of them, any court of equitable jurisdiction within
the State of Delaware may, on the application in a summary way of the
Corporation or of any creditor or stockholder thereof or on the application of
any receiver or receivers appointed for the Corporation under Section 291 of the
Delaware General Corporation Law or on the application of trustees in
dissolution or of any receiver or receivers appointed for the Corporation under
Section 279 of the Delaware General Corporation Law, order a meeting of the
creditors or class of creditors, and/or of the stockholders or class of
stockholders of the Corporation, as the case may be, to be summoned in such
manner as such court directs. If a majority in number representing three-fourths
in value of the creditors or class of creditors, and/or of the stockholders or
class of stockholders of the Corporation, as the case may be, agree to any
compromise or arrangement and to any reorganization of the Corporation as a
consequence of such compromise or arrangement, then such compromise or
arrangement and such reorganization shall, if sanctioned by the court to which
such application has been made, be binding on all the creditors or class of
creditors, and/or on all of the stockholders or class of stockholders of the
Corporation, as the case may be, and also on the Corporation.

                                    ARTICLE X

                             LIMITATION OF LIABILITY

     No director of the Corporation shall be liable to the Corporation or its
stockholders for monetary damages for breach of his or her fiduciary duty as
director; PROVIDED, HOWEVER, that nothing contained in this Article X shall
eliminate or limit the liability of a director:

                (a)    for any breach of the director's duty of loyalty to the
Corporation or its stockholders;

                (b)    for acts or omissions not in good faith or which involve
intentional misconduct or a knowing violation of the law;

                (c)    under Section 174 of the General Corporation Law of the
State of Delaware; or

                (d)    for any transaction from which the director derived
improper personal benefit.

     No amendment to or repeal of this Article X shall apply to or have any
effect on the liability or alleged liability of any director of the Corporation
for or with respect to any acts or omissions of such director occurring prior to
such amendment or repeal.

                                     - 29 -
<Page>

                                   ARTICLE XI

                                 INDEMNIFICATION

     1.   ACTIONS, SUITS AND PROCEEDINGS OTHER THAN BY OR IN THE RIGHT OF THE
CORPORATION. The Corporation shall indemnify each person who was or is a party
or is threatened to be made a party to any threatened, pending or completed
action, suit or proceeding, whether civil, criminal, administrative or
investigative (other than an action by or in the right of the Corporation), by
reason of the fact that he is or was, or has agreed to become, a director or
officer of the Corporation, or is or was serving, or has agreed to serve, at the
request of the Corporation, as a director, officer or trustee of, or in a
similar capacity with, another corporation, partnership, joint venture, trust or
other enterprise (including any employee benefit plan) (all such persons being
referred to hereafter as an "Indemnitee"), or by reason of any action alleged to
have been taken or omitted in such capacity, against all expenses (including
attorneys' fees), judgments, fines and amounts paid in settlement actually and
reasonably incurred by him or on his behalf in connection with such action, suit
or proceeding and any appeal therefrom, if he acted in good faith and in a
manner he reasonably believed to be in, or not opposed to, the best interests of
the Corporation, and, with respect to any criminal action or proceeding, had no
reasonable cause to believe his conduct was unlawful. The termination of any
action, suit or proceeding by judgment, order, settlement, conviction or upon a
plea of NOLO CONTENDERE or its equivalent, shall not, of itself, create a
presumption that the person did not act in good faith and in a manner which he
reasonably believed to be in, or not opposed to, the best interests of the
Corporation, and, with respect to any criminal action or proceeding, had
reasonable cause to believe that his conduct was unlawful. Notwithstanding
anything to the contrary in this Article, except as set forth in Section 7
below, the Corporation shall not indemnify an Indemnitee seeking indemnification
in connection with a proceeding (or part thereof) initiated by the Indemnitee
unless the initiation thereof was approved by the Board of Directors of the
Corporation. Notwithstanding anything to the contrary in this Article, the
Corporation shall not indemnify an Indemnitee to the extent such Indemnitee is
reimbursed from the proceeds of insurance, and in the event the Corporation
makes any indemnification payments to an Indemnitee and such Indemnitee is
subsequently reimbursed from the proceeds of insurance, such Indemnitee shall
promptly refund such indemnification payments to the Corporation to the extent
of such insurance reimbursement.

     2.   ACTIONS OR SUITS BY OR IN THE RIGHT OF THE CORPORATION. The
Corporation shall indemnify any Indemnitee who was or is a party or is
threatened to be made a party to any threatened pending or completed action or
suit by or in the right of the Corporation to procure a judgment in its favor by
reason of the fact that he is or was, or has agreed to become, a director or
officer of the Corporation, or is or was serving, or has agreed to serve, at the
request of the Corporation, as a director, officer or trustee of, or in a
similar capacity with, another corporation, partnership, joint venture, trust or
other enterprise (including any employee benefit plan), or by reason of any
action alleged to have been taken or omitted in such capacity, against all
expenses (including attorneys' fees) and, to the extent permitted by law,
amounts paid in settlement actually and reasonably incurred by him or on his
behalf in connection with such action, suit or proceeding and any appeal
therefrom, if he acted in good faith and in a manner he reasonably believed to
be in, or not opposed to, the best interests of the Corporation, except that no
indemnification shall be made in respect of any claim, issue or matter as to
which such person

                                     - 30 -
<Page>

shall have been adjudged to be liable to the Corporation unless and only to the
extent that the Court of Chancery of Delaware shall determine upon application
that, despite the adjudication of such liability but in view of all the
circumstances of the case, such person is fairly and reasonably entitled to
indemnity for such expenses (including attorneys' fees) which the Court of
Chancery of Delaware shall deem proper.

     3.   INDEMNIFICATION FOR EXPENSES OF SUCCESSFUL PARTY. Notwithstanding the
other provisions of this Article, to the extent that an Indemnitee has been
successful, on the merits or otherwise, in defense of any action, suit or
proceeding referred to in Sections 1 and 2 of this Article, or in defense of any
claim, issue or matter therein, or on appeal from any such action, suit or
proceeding, he shall be indemnified against all expenses (including attorneys'
fees) actually and reasonably incurred by him or on his behalf in connection
therewith. Without limiting the foregoing, if any action, suit or proceeding is
disposed of, on the merits or otherwise (including a disposition without
prejudice), without (i) the disposition being adverse to the Indemnitee, (ii) an
adjudication that the Indemnitee was liable to the Corporation, (iii) a plea of
guilty or NOLO CONTENDERE by the Indemnitee, (iv) an adjudication that the
Indemnitee did not act in good faith and in a manner he reasonably believed to
be in or not opposed to the best interests of the Corporation, and (v) with
respect to any criminal proceeding, an adjudication that the Indemnitee had
reasonable cause to believe his conduct was unlawful, the Indemnitee shall be
considered for the purposes hereof to have been wholly successful with respect
thereto.

     4.   NOTIFICATION AND DEFENSE OF CLAIM. As a condition precedent to his
right to be indemnified, the Indemnitee must notify the Corporation in writing
as soon as practicable of any action, suit, proceeding or investigation
involving him for which indemnity will or could be sought. With respect to any
action, suit, proceeding or investigation of which the Corporation is so
notified, the Corporation will be entitled to participate therein at its own
expense and/or to assume the defense thereof at its own expense, with legal
counsel reasonably acceptable to the Indemnitee. After notice from the
Corporation to the Indemnitee of its election so to assume such defense, the
Corporation shall not be liable to the Indemnitee for any legal or other
expenses subsequently incurred by the Indemnitee in connection with such claim,
other than as provided below in this Section 4. The Indemnitee shall have the
right to employ his own counsel in connection with such claim, but the fees and
expenses of such counsel incurred after notice from the Corporation of its
assumption of the defense thereof shall be at the expense of the Indemnitee
unless (i) the employment of counsel by the Indemnitee has been authorized by
the Corporation, (ii) counsel to the Indemnitee shall have reasonably concluded
that there may be a conflict of interest or position on any significant issue
between the Corporation and the Indemnitee in the conduct of the defense of such
action or (iii) the Corporation shall not in fact have employed counsel to
assume the defense of such action, in each of which cases the fees and expenses
of counsel for the Indemnitee shall be at the expense of the Corporation, except
as otherwise expressly provided by this Article. The Corporation shall not be
entitled, without the consent of the Indemnitee, to assume the defense of any
claim brought by or in the right of the Corporation or as to which counsel for
the Indemnitee shall have reasonably made the conclusion provided for in clause
(ii) above.

     5.   ADVANCE OF EXPENSES. Subject to the provisions of Section 6 below, in
the event that the Corporation does not assume the defense pursuant to Section 4
of this Article of any action, suit, proceeding or investigation of which the
Corporation receives notice under this

                                     - 31 -
<Page>

Article, any expenses (including attorneys' fees) incurred by an Indemnitee in
defending a civil or criminal action, suit, proceeding or investigation or any
appeal therefrom shall be paid by the Corporation in advance of the final
disposition of such matter; PROVIDED, HOWEVER, that the payment of such expenses
incurred by an Indemnitee in advance of the final disposition of such matter
shall be made only upon receipt of an undertaking by or on behalf of the
Indemnitee to repay all amounts so advanced in the event that it shall
ultimately be determined that the Indemnitee is not entitled to be indemnified
by the Corporation as authorized in this Article. Such undertaking shall be
accepted without reference to the financial ability of the Indemnitee to make
such repayment.

     6.   PROCEDURE FOR INDEMNIFICATION. In order to obtain indemnification or
advancement of expenses pursuant to Section 1, 2, 3 or 5 of this Article, the
Indemnitee shall submit to the Corporation a written request, including in such
request such documentation and information as is reasonably available to the
Indemnitee and is reasonably necessary to determine whether and to what extent
the Indemnitee is entitled to indemnification or advancement of expenses. Any
such indemnification or advancement of expenses shall be made promptly, and in
any event within 60 days after receipt by the Corporation of the written request
of the Indemnitee, unless with respect to requests under Section 1, 2 or 5 the
Corporation determines within such 60-day period that the Indemnitee did not
meet the applicable standard of conduct set forth in Section 1 or 2, as the case
may be. Such determination shall be made in each instance by (a) a majority vote
of the directors of the Corporation consisting of persons who are not at that
time parties to the action, suit or proceeding in question ("disinterested
directors"), whether or not a quorum, (b) a majority vote of a quorum of the
outstanding shares of stock of all classes entitled to vote for directors,
voting as a single class, which quorum shall consist of stockholders who are not
at that time parties to the action, suit or proceeding in question, (c)
independent legal counsel (who may, to the extent permitted by law, be regular
legal counsel to the Corporation), or (d) a court of competent jurisdiction.

     7.   REMEDIES. The right to indemnification or advances as granted by this
Article shall be enforceable by the Indemnitee in any court of competent
jurisdiction if the Corporation denies such request, in whole or in part, or if
no disposition thereof is made within the 60-day period referred to above in
Section 6. Unless otherwise required by law, the burden of proving that the
Indemnitee is not entitled to indemnification or advancement of expenses under
this Article shall be on the Corporation. Neither the failure of the Corporation
to have made a determination prior to the commencement of such action that
indemnification is proper in the circumstances because the Indemnitee has met
the applicable standard of conduct, nor an actual determination by the
Corporation pursuant to Section 6 that the Indemnitee has not met such
applicable standard of conduct, shall be a defense to the action or create a
presumption that the Indemnitee has not met the applicable standard of conduct.
The Indemnitee's expenses (including attorneys' fees) incurred in connection
with successfully establishing his right to indemnification, in whole or in
part, in any such proceeding shall also be indemnified by the Corporation.

     8.   SUBSEQUENT AMENDMENT. No amendment, termination or repeal of this
Article or of the relevant provisions of the General Corporation Law of Delaware
or any other applicable laws shall affect or diminish in any way the rights of
any Indemnitee to indemnification under the provisions hereof with respect to
any action, suit, proceeding or investigation arising out of

                                     - 32 -
<Page>

or relating to any actions, transactions or facts occurring prior to the final
adoption of such amendment, termination or repeal.

     9.   OTHER RIGHTS. The indemnification and advancement of expenses provided
by this Article shall not be deemed exclusive of any other rights to which an
Indemnitee seeking indemnification or advancement of expenses may be entitled
under any law (common or statutory), agreement or vote of stockholders or
disinterested directors or otherwise, both as to action in his official capacity
and as to action in any other capacity while holding office for the Corporation,
and shall continue as to an Indemnitee who has ceased to be a director or
officer, and shall inure to the benefit of the estate, heirs, executors and
administrators of the Indemnitee. Nothing contained in this Article shall be
deemed to prohibit, and the Corporation is specifically authorized to enter
into, agreements with officers and directors providing indemnification rights
and procedures different from those set forth in this Article. In addition, the
Corporation may, to the extent authorized from time to time by its Board of
Directors, grant indemnification rights to other employees or agents of the
Corporation or other persons serving the Corporation and such rights may be
equivalent to, or greater or less than, those set forth in this Article.

     10.  PARTIAL INDEMNIFICATION. If an Indemnitee is entitled under any
provision of this Article to indemnification by the Corporation for some or a
portion of the expenses (including attorneys' fees), judgments, fines or amounts
paid in settlement actually and reasonably incurred by him or on his behalf in
connection with any action, suit, proceeding or investigation and any appeal
therefrom but not, however, for the total amount thereof, the Corporation shall
nevertheless indemnify the Indemnitee for the portion of such expenses
(including attorneys' fees), judgments, fines or amounts paid in settlement to
which the Indemnitee is entitled.

     11.  INSURANCE. The Corporation may purchase and maintain insurance, at its
expense, to protect itself and any director, officer, employee or agent of the
Corporation or another corporation, partnership, joint venture, trust or other
enterprise (including any employee benefit plan) against any expense, liability
or loss incurred by him in any such capacity, or arising out of his status as
such, whether or not the Corporation would have the power to indemnify such
person against such expense, liability or loss under the General Corporation Law
of Delaware.

     12.  CONSOLIDATION. If the Corporation is merged into or consolidated with
another corporation and the Corporation is not the surviving corporation, the
surviving corporation shall assume the obligations of the Corporation under this
Article with respect to any action, suit, proceeding or investigation arising
out of or relating to any actions, transactions or facts occurring prior to the
date of such merger or consolidation.

     13.  SAVINGS CLAUSE. If this Article or any portion hereof shall be
invalidated on any ground by any court of competent jurisdiction, then the
Corporation shall nevertheless indemnify each Indemnitee as to any expenses
(including attorneys' fees), judgments, fines and amounts paid in settlement in
connection with any action, suit, proceeding or investigation, whether civil,
criminal or administrative, including an action by or in the right of the
Corporation, to the fullest extent permitted by any applicable portion of this
Article that shall not have been invalidated and to the fullest extent permitted
by applicable law.

                                     - 33 -
<Page>

     14.  DEFINITIONS.  Terms used herein and defined in Section 145(h) and
Section 145(i) of the General Corporation Law of Delaware shall have the
respective meanings assigned to such terms in such Section 145(h) and Section
145(i).

     15.  SUBSEQUENT LEGISLATION. If the General Corporation Law of Delaware is
amended after adoption of this Article to expand further the indemnification
permitted to Indemnitees, then the Corporation shall indemnify such persons to
the fullest extent permitted by the General Corporation Law of Delaware, as so
amended.

                                     - 34 -
<Page>

     IN WITNESS WHEREOF, the undersigned has caused this Sixth Restated
Certificate Of Incorporation to be duly executed on its behalf as of November
20, 2001.

                                   NITROMED, INC.


                                   By:  /s/ Michael D. Loberg
                                      -----------------------------
                                   Michael D. Loberg
                                   Chief Executive Officer

                                     - 35 -
<Page>

                            CERTIFICATE OF AMENDMENT

                                       OF

                   SIXTH RESTATED CERTIFICATE OF INCORPORATION

                                       OF

                                 NITROMED, INC.


                             PURSUANT TO SECTION 242

                        OF THE GENERAL CORPORATION LAW OF

                              THE STATE OF DELAWARE

     NitroMed, Inc. (hereinafter called the "Corporation"), organized and
existing under and by virtue of the General Corporation Law of the State of
Delaware, does hereby certify as follows:

     At a meeting of the Board of Directors of the Corporation a resolution was
duly adopted, pursuant to Section 242 of the General Corporation Law of the
State of Delaware, setting forth an amendment to the Certificate of
Incorporation of the Corporation and declaring said amendment to be advisable.
The stockholders of the Corporation duly approved said proposed amendment by
written consent in accordance with Sections 228 and 242 of the General
Corporation Law of the State of Delaware. The resolutions setting forth the
amendment are as follows:

     RESOLVED: That Section A.6(c)(iv)(B) of Article III of the Sixth Restated
Certificate of Incorporation of the Corporation be and hereby is deleted in its
entirety and the following is inserted in lieu thereof:

     "(B) entered into pursuant to the 1993 Equity Incentive Plan of the
     Corporation, as amended with requisite Board and Stockholder approvals from
     time to time, (the "1993 Equity Incentive Plan"), the 2003 Stock Incentive
     Plan of the Corporation, as amended with requisite Board and Stockholder
     approvals from time to time, (the "2003 Stock Incentive Plan"), or any
     stock option plan which has been adopted by the Corporation and approved by
     the Board of Directors and by the holders of at least a majority of the
     combined voting power of the Series Preferred Stock then outstanding
     (including any outstanding shares of Common Stock issued upon conversion
     thereof), and the forms of option agreements under the 1993 Equity
     Incentive Plan and 2003 Stock Incentive Plan are satisfactory in form and
     in substance, except for immaterial changes thereto may from time to time
     by officers of the Corporation, to the Board of Directors and to the
     holders of at least a majority of the combined voting power of the Series
     Preferred Stock then

<Page>

     outstanding (including any outstanding shares of Common Stock issued upon
     conversion thereof),"

     RESOLVED: That Section A.6(c)(x) of Article III of the Sixth Restated
Certificate of Incorporation of the Corporation be and hereby is deleted in its
entirety and the following is inserted in lieu thereof:

     "amend, modify or terminate the 1993 Equity Incentive Plan, amend, modify
     or terminate the 2003 Stock Incentive Plan, or amend or modify any stock
     option agreement or restricted stock purchase agreement entered into
     between the Corporation and its employees, directors or consultants, except
     for immaterial changes made thereto from time to time by officers of the
     Corporation; or"

     RESOLVED: That Section A.7(d)(iv)(B) of Article III of the Sixth Restated
Certificate of Incorporation of the Corporation be and hereby is deleted in its
entirety and the following is inserted in lieu thereof:

     "A.7(d)(iv)(B) Common Stock issued or issuable to officers, directors or
     employees of or consultants or independent contractors to the Corporation,
     pursuant to any written agreement, plan or arrangement, including pursuant
     to any option granted under the 1993 Equity Incentive Plan, as amended, or
     the 2003 Stock Incentive Plan to purchase, or rights to subscribe for, such
     Common Stock, that is set forth on Schedule 5.2 to the Series F Stock
     Purchase Agreement or that has been approved in form and substance by the
     holders of at least a majority of the combined voting power of the Series
     Preferred Stock then outstanding (determined in accordance with Section
     A.6(a) hereof and including in such calculation any shares of Series
     Preferred Stock which have been converted by the holder thereof into shares
     of the Corporation's Common Stock), and which, as a condition precedent to
     the issuance of such shares, provides for the vesting of such shares and
     subjects such shares to restrictions on transfers and rights of first offer
     or refusal in favor of the Corporation on terms that have been approved by
     the holders of at least a majority of the combined voting power of the
     Series Preferred Stock then outstanding (determined in accordance with
     Section A.6(a) hereof and including in such calculation any shares of
     Series Preferred Stock which have been converted by the holder thereof into
     Shares of the Corporation's Common Stock) (collectively, the "Required
     Terms"), unless any of such Required Terms are waived by holders of shares
     representing at least a majority of the voting power of the Series
     Preferred Stock then outstanding (determined as set forth in Section A.6(a)
     hereof);"

     IN WITNESS WHEREOF, the Corporation has caused this Certificate of
Amendment to be signed by its Chief Executive Officer this 12th day of May,
2003.

                                   NITROMED, INC.


                                   By:/s/ Michael D. Loberg
                                      -------------------------
                                      Michael D. Loberg
                                      Chief Executive Officer

<Page>

                            CERTIFICATE OF AMENDMENT
                                       OF
                   SIXTH RESTATED CERTIFICATE OF INCORPORATION
                                       OF
                                 NITROMED, INC.

     The Directors of the Corporation duly approved an amendment to the Sixth
Restated Certificate of Incorporation at a regular meeting of the Board of
Directors of the Corporation in accordance with Sections 141 and 242 of the
General Corporation Law of the State of Delaware. The stockholders of the
Corporation duly adopted the amendment to the Sixth Restated Certificate of
Incorporation of the Corporation in accordance with Sections 228 and 242 of the
General Corporation Law of the State of Delaware, and written notice of such
consent will be given to all stockholders who have not consented in writing to
said amendment. The resolution setting forth this amendment is as follows:

RESOLVED:      That the Sixth Restated Certificate of Incorporation of the
               Corporation be amended by deleting the first paragraph of Article
               III in its entirety and inserting the following in lieu thereof:

               (a)  AUTHORIZATION.  The total number of shares of all classes of
               stock which the Corporation shall have authority to issue is
               56,362,798, consisting of:

                    (i) 34,688,320 shares of Preferred Stock, par value $.01 per
               share (the "Preferred Stock"), of which:

                          (A) 5,000,000 shares shall be designated "Series A
               Convertible Preferred Stock" (the "Series A Stock");

                          (B) 17,005,330 shares shall be designated "Series B
               Convertible Preferred Stock" (the "Series B Stock");

                          (C) 3,157,895 shares shall have been designated
               "Series C Convertible Preferred Stock" (the "Series C Stock");

                          (D) 2,137,791 shares shall have been designated
               "Series D Convertible Preferred Stock" (the "Series D Stock");

                          (E) 7,137,304 shares shall have been designated
               "Series E Convertible Preferred Stock" (the "Series E Stock");

                          (F) 250,000 shares shall have been designated "Series
               F Junior Convertible Preferred Stock" (the Series F Junior
               Stock"); and

                    (ii) 21,674,478 shares of Common Stock, par value $.01 per
               share (the "Common Stock").

<Page>

IN WITNESS WHEREOF, the Corporation has caused this Certificate of Amendment to
be signed by its Chief Financial Officer on this 31st day of July, 2003.

                                   NITROMED, INC.


                                   By:/s/ Joseph Grimm
                                      --------------------------
                                      Joseph Grimm
                                      Chief Financial Officer